The field of condensed matter physics, which overlaps with chemistry, materials science and engineering, attempts to understand the physical properties of materials. This includes a broad range of topics including but not limited to:
- Structural, Electronic, Dielectric, Electrical, Magnetic, and Optical Properties of Materials;
- Novel Quantum Materials – superconductors, topological insulators, Weyl semimetals and quantum spin liquids;
- Magnetoelectric and multiferroic materials;
- 2D and 3D Magnetic Systems;
- Quantum Hall Effect;
- Energetic Materials
- Semiconductors, Photovoltaics, Optoelectronics and Photonics;
- Magneto-Transports, Magnetic Interfaces and Spintronics;
- Complex Oxides and Emergent Phenomena.
Topological Photo-current and magnetization control in 3D Topological Insulators
Optical control of helicity-dependent photocurrent has also been studied in 3D topological insulators. Strong spin-orbit coupling and spin-momentum locking make this system unique for their applications. We observed that photocurrent can be controlled by exciting the sample with different circular and linear polarized light, yielding a polarization-dependent current density which can be fitted very well with a theoretical model. This photocurrent can also be controlled with the help of photo-thermal gradient generated by the excitation light beam. Enhancement and inversion of this photocurrent in presence of photo-thermal gradient for light incident on two opposite edges of the sample occur due to selective spin state excitation with two opposite (left and right) circularly polarized light in presence of the unique spin-momentum locked surface states. We also present efficient spin to charge conversion (SCC) in the topological insulator and ferromagnetic thin films based heterostructure by using spin-pumping technique The SCC, characterized by inverse Edelstein effect length (kIEE) in the TI material, gets altered with an intervening Copper (Cu) layer, and it depends on the interlayer thickness. The introduction of Cu layer at the interface of TI and FM metal provides a new degree of freedom for tuning the SCC efficiency of the topological surface states. The significant enhancement of the measured spin-pumping voltage and the increased linewidth of ferromagnetic resonance absorption spectra due to the insertion of Cu layer at the interface indicate a reduction in spin memory loss at the interface that resulted from the presence of exchange coupling between the surface states of TI and the local moments of FM metal.
Binary Actinide Oxides: Synthesis, Crystal Structures, and Magnetic Properties
Actinides, with their distinctive electronic configurations, play a crucial role in the advancement of quantum phenomena research and the nuclear industry, promising significant technological advancements. These elements exhibit the dual nature of 5f-states, competing interactions, and strong spin-orbit coupling, leading to complex magnetic behaviors such as multi-k antiferromagnetic ordering, multipolar ordering, and mixed valence configurations. The structural and magnetic properties of actinide systems are a focal point due to their intriguing nature. Despite the allure of their properties, research has been limited by their toxicity, radioactivity, and high reactivity. Traditionally, studies on actinide oxides have primarily focused on uranium and plutonium compounds within nuclear fuel contexts. However, the physical properties of other actinide oxides remain underexplored. This presentation will cover the synthesis methods for selected binary actinide oxides, including dioxides and sesquioxides, and provide insights into their current understanding of crystal structures. Additionally, the talk will address the challenges in unraveling the magnetic properties of these oxides, aiming to foster a deeper comprehension of their complex phenomena.
Please look below for detailed schedule.
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Abstract Number: ANPA2024-N00029 Presenting Author: Sabita Pandey Presenter's Affiliation: Central Department of Physics, Tribhuvan University, Kirtipur, 44613 Kathmandu, Nepal Title: Electronic and Magnetic Properties of Honeycomb Layered Oxide: Na3Mn2SbO6 Location: Poster Presentation Show/Hide Abstract Electronic and Magnetic Properties of Honeycomb Layered Oxide: Na3Mn2SbO6
Sabita Pandey1,2*; Pratima Khadka1,2; Sarita Lawaju1,2, and Madhav Prasad Ghimire1
1Central Department of Physics, Tribhuvan University, Kirtipur, 44613 Kathmandu, Nepal
2Condensed Matter Physics Research Center (CMPRC) Butwal, Rupandehi, Nepal.
*sabita.775511@cdp.tu.edu.np
Abstract
The electronic and magnetic properties of Na3Mn2SbO6 (NMSO), a honeycomb layered oxide, were explored through density functional theory (DFT) using the full-potential local orbital (FPLO) code. The monoclinc (C2/m) NMSO consists of honeycomb layers (Mn2SbO6)3- formed by the 2:1 ordering of Mn and Sb, which then form honeycomb patterns. The results of our calculations using generalized gradient approximation (GGA) as the exchange-correlation potential confirmed the oxide is an anti-ferromagnet with a direct band gap of 0.38765 eV. The band gap is contributed by the Mn-3d state in valence band and Sb-5s states in conduction band. The crystal and band structures were affected by the geometry optimization. Oxides such as NMSO garner immense interest from researchers due to their potential applications as high-energy storage devices.
Keywords: Honeycomb layered oxides, monoclinic, antiferromagnet, direct band gap, energy storage device
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Abstract Number: ANPA2024-N00028 Presenting Author: Pawan Joshi Presenter's Affiliation: Central Department of Physics, Tribhuvan University, Kirtipur 44613, Kathmandu, Nepal Title: Electronic and Thermoelectric Properties of Kagome Rb2Pt3S4 Location: Poster Presentation Show/Hide Abstract We performed the theoretical investigation of electronic and thermoeletric properties of a kagome material Rb2Pt3S4 based on density functional theory using the full potential linearized augmented plane wave plus local orbitals (FP-LAPW+lo) method with in the frame work of GGA and TB-mBJ exchange-correlation potential. From the electronic structure study, we found that Rb2Pt3S4 is an indirect band gap semiconductor with an energy gap 1.29 (1.87) eV using GGA(TB-mBJ). The semi-classical Boltzmann transport theory were employed to study the charge-carrier transport behavior and temperature dependent thermoelectric (TE) properties, including Seebeck coefficient, electrical conductivity, electronic thermal conductivity, power factor, and figure of merit. Our reported results show that the material is beneficial for n-type TE material at high temperature as n-type transport parameters are greater than the p-type ones. The maximum values of the figure of merit for the title compound were computed corresponding to optimum n(p)-type doping concentrations. These important parameters are noteworthy to explore experimental works for real time application of studied compound as TE material.
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Abstract Number: ANPA2024-N00027 Presenting Author: Meenashree Khanal Presenter's Affiliation: Department of Physics, Amrit Campus, Tribhuvan University Title: Effect of UV light on impedance spectrum of the pure and Ag-doped ZnO film Location: Poster Presentation Show/Hide Abstract This work reports the impedance spectrum analysis of the undoped and silver-doped ZnO film before and after UV treatment. UV light of wavelength 365 nm was exposed on ZnO and Ag-ZnO films and their impedance data was recorded using a Hioki LCR meter in the AC frequency range of 100 Hz to 10,000 Hz. Herein, the spin coating method was employed to synthesize undoped and 1% to 5% Ag-doped ZnO films. The structural, optical and UV light sensing properties of as-prepared films were investigated employing XRD, UV-Vis spectrophotometer, and FTIR techniques. The X-ray diffraction pattern results demonstrated the polycrystalline, hexagonal wurtzite nature of ZnO of crystallite size ~25.4 nm and Zn-O bond length of 1.95 Å . The results also showed a gradual decrease in size from 26.44 nm for 3% and 24.19 nm for 5% Ag-doped ZnO film. On the other hand, the band gap calculated from observed transmittance showed the average band gap of ZnO was 3.22 eV. The impedance spectrum analysis of ZnO before and after UV exposure showed a decrease in the diameter of the Nyquist arc which indicates an increase in the film’s conductivity. These characteristics of ZnO are found to be useful for potential semiconductor devices and optical sensors.
Keywords: ZnO film, Ag-ZnO, spin coating, UV light, impedance spectrum
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Abstract Number: ANPA2024-N00026 Presenting Author: Manisha Rai Presenter's Affiliation: Student Title: STUDY ON POROUS Al DOPED ZnO THIN FILM AS A GLUCOSE BIOSENSOR Location: Poster Presentation Show/Hide Abstract This work reports on the development of a novel and efficient non-enzymatic porous Al-doped porous ZnO glucose sensor. The thin film of ZnO with different percent of Al doping were synthesized by using spin coating method, on the steel substrate. The prepared sample were characterized by optical study and nyquist plot. Cyclic voltammetry was used to analyze and optimize the electrochemical performance. CV measurements showed that, 2% Al-doped thin film showed better resultant current in the basic medium. Additionally, different percentages of PEG were added into the ZnO precursor solution to fabricate the porous ZnO film. The 6% PEG was optimized to perform the best electrochemical activity. The 2%Al-ZnO/steel sample showed a 62.5µM low detection limit (LOD); however, porous 6%PEG+2\%Al-ZnO/steel showed an improved LOD of 0.122µM. Nyquist plots showed that the enhanced performance of of 6%PEG+2%Al-ZnO/steel sample is due to improved charge transfer resistance.
Keywords : Non-Enzymatic, Biosensor, ZnO, Thin Film
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Abstract Number: ANPA2024-N00025 Presenting Author: Kedar Nath Jaiswal Presenter's Affiliation: Central Department of Physics,Kirtipur,Kathmandu Title: Electronic and Optical Property Tuning by Chlorine Doping on Oxyhalide Bi2LaO4I Location: Poster Presentation Show/Hide Abstract Electronic and Optical Property Tuning by Chlorine Doping on Oxyhalide Bi2LaO4I
Kedar Nath Jaiswal1,2, Sarita Lawaju1,2 and Madhav Prasad Ghimire1,3,4*
1Central Department of Physics, Tribhuvan University, Kirtipur, 44613 Kathmandu, Nepal
2Condensed Matter Physics Research Center (CMPRC) Butwal, Rupandehi, Nepal.
3Leibniz - IFW Dresden,Helmholtzstr. 20, 01069 Dresden, Germany
4Faculty of Science Education, Jeju National University, Jeju 63243, Republic of Korea
*Corresponding author: madhav.ghimire@cdp.tu.edu.np
ABSTRACT
Layered Bismuth oxyhalides are promising photocatalysts used for the degradation of organic molecules as well as for water splitting reaction. The photocatalytic activity of pristine layered Bi2LaO4I as well as Cl doped Bi2LaO4I were investigated on the basis of full-potential local orbital (FPLO), adopting both the scalar relativistic formulations within the framework of the generalized gradient approximation(GGA) and modified Becke and Johnson (mBJ) as exchange-correlation potential. Our calculations confirm the increase in band gap of Bi2LaO4I from 1.0811eV to 1.1437 eV (within GGA) and from 1.8784 eV to 1.8848 eV (within GGA-mBJ) when Cl is doped. Further, we conclude that the optical band gap of these oxyhalides can be tuned through concentration of Cl doped in them.
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Abstract Number: ANPA2024-N00024 Presenting Author: Dipak Oli Presenter's Affiliation: Tribhuvan University, Kathmandu Nepal Title: FIRST PRINCIPLES STUDY OF UNDOPED AND HALOGEN DOPED ZnO MONOLAYER Location: Poster Presentation Show/Hide Abstract Addition of impurities in pristine 2D materials has been one of the recent trends. The physical properties of materials have been greatly enhanced by doping with foreign elements and creating vacancies. In this work, we studied structural, electronic, and magnetic properties of undoped and halogen (F, Cl, Br) doped ZnO monolayer, whereas one Zn-atom is replaced by a halogen atom. Computation was done using Density Functional Theory in VASP computational tool. The PBE and PBE+U functionals were employed in order to study the exchange correlation functional. The band gap of pure ZnO was found to be 1.67 eV and 2.61 eV while employing PBE and PBE+U functionals respectively. However, the band gap was found to be sharply decreased, suggesting that the conductivity of the doped monolayer increases. Further, analyzing the Density of state (DoS) and projected Density of state (PDoS) of our systems, it was found that the halogen doped ZnO behaves like a magnetic material.
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Abstract Number: ANPA2024-N00022 Presenting Author: Damodar Neupane Presenter's Affiliation: Patan Multiple Campus, Tribhuvan University Title: Comparative Study of Titanium Dioxide and Lysozyme-Doped Titanium Dioxide Nanoparticles for Enhanced Photocatalytic Degradation Location: Poster Presentation Show/Hide Abstract Titanium dioxide (TiO2) and lysozyme-doped titanium dioxide (L-TiO2) nanoparticles were synthesized via a hydrothermal method. Structural, morphological and optical properties of L-TiO2 were compared with synthesized TiO2 nanoparticles prepared without lysozyme. X-ray diffraction (XRD) patterns revealed the dominance of the anatase phase and presence of rarely found α-PbO2 structure in L-TiO2, while TiO2 exhibited anatase, brookite and rutile phases. Both nanoparticles possess fewer structural defects, potentially enhancing mechanical properties. Fourier transform infrared spectroscopy (FTIR) identified specific chemical bonds or functional groups associated with lysozyme addition. UV-Vis spectroscopy indicated a decrease in the band gap energy from 3.21 to 2.94 eV upon the incorporation of lysozyme on titanium dioxide nanoparticle. High Resolution Transmission Electron Microscopy (HR-TEM) analysis confirmed an average particle size of 9.18 nm for L-TiO2 and 22.97 nm for TiO2 nanoparticles, consistent with XRD results. Field Emission Scanning Electron Microscopy (FE-SEM/EDS) analysis showed agglomerated fine particles with the presence of Ti, O, and C elements. L-TiO2 nanoparticles showed enhanced photocatalytic performance, degrading Methylene Blue dye to 97% with a rate constant of 0.039 min-1 and Methyl Orange to 81% with a rate constant of 0.019 min-1 within a 90 minute time interval under UV irradiation at 365 nm, compared to 90% and 76% degradation, using TiO2 nanoparticles. Optimization studies revealed that the best degradation efficiency was achieved at a dosage of 0.1 g. Additionally, the synthesis process produced TiO2 polymorphs, including α-PbO2-type TiO2, which showed superior photocatalytic activity. L-TiO demonstrated superior reusability compared to TiO2 for both dyes, maintaining consistent degradation on repeated cycles. Overall, the study highlights the potential of L-TiO2 nanoparticles for environmental applications.
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Abstract Number: ANPA2024-N00021 Presenting Author: Bikal Khanal Presenter's Affiliation: Central Department of Physics, Tribhuvan University Title: A Review on Machine Learning for Design, Discovery and Properties of Energy Materials Location: Poster Presentation Show/Hide Abstract Materials design and property prediction based on structure have recently become an important area in energy materials research. This marks a transition in exploration methodologies, moving away from traditional approaches often constrained by time-consuming empiricism and experiments, resulting in slow progress in research and development. An innovative strategy is considered necessary to accelerate this process by leveraging new technologies for discovery and advancement. A new paradigm involving the utilization of Artificial Intelligence (AI) and Machine Learning (ML) in materials research is emerging. This approach centered on data facilitates the engineering of new energy materials and the prediction of their properties without depending on conventional techniques. Several studies show advancements in materials engineering, design improvements, the utilization of energy materials, and more by deploying ML. This article revisits the established three paradigms of energy materials research and contrasts them with this emerging fourth paradigm. It delivers a concise outline of ML methodologies, databases utilized for energy materials, and a comparative evaluation of various ML models to elucidate the present research trajectory. The advantages and constraints presented by AI and ML in the design and advancement of different energy materials such as Li-Ion batteries, photovoltaic materials, CO2 capture materials, among others are demonstrated. Finally, a number of successful cases are outlined where ML has demonstrated its reliability as a research tool in the research and development of energy materials.
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Abstract Number: ANPA2024-N00023 Presenting Author: Dikshya Chand Presenter's Affiliation: Physics, M.Sc., Patan Multiple Campus Title: Development of Non-Enzymatic Glucose Biosensor using Cobalt Oxide Thin Film Location: Poster Presentation Show/Hide Abstract Development of Non-Enzymatic Glucose Biosensor using Cobalt Oxide Thin film
Dikshya Chand1, Manisha Rai1, Leela Pradhan Joshi2, Shankar Prasad Shrestha1
1Physics Department, Patan Multiple Campus, Lalitpur, Tribhuvan University, Nepal
2Physics Department, Amrit Campus, Tribhuvan University,
Email: shankarpds@yahoo.com
In the present work, cobalt oxide thin films were fabricated via a spray pyrolysis technique and studied their application in glucose detection using cyclic voltammetry (CV). Cobalt oxide thin films were deposited on steel substrate at 150±50 degree C. The structural properties of cobalt oxide thin films were studied using X-ray diffraction. The electrochemical performance of the cobalt oxide thin films for glucose detection was evaluated using cyclic voltammetry. The cobalt oxide based sensor exhibited a significant electrochemical response to glucose. Herein, we optimized various factors like concentration of electrolyte, deposition temperature, number of coatings and scan rate. The result showed that 0.7 M concentration of KOH solution, deposition temperature of 150 ±50 degree C, 12 coated layer and scan rate of 40 mV/s as the best result condition. These findings suggest that spray deposited cobalt oxide thin films are promising candidates for non-enzymatic glucose sensors, offering a potential pathway for developing cost-effective glucose monitoring devices.
Keywords: Cobalt oxide, Thin films, Spray pyrolysis, Cyclic voltammetry, Glucose detection, Non-enzymatic sensor.
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Abstract Number: ANPA2024-N00037 Presenting Author: Chiranjib Mitra (Invited) Presenter's Affiliation: Indian Institute of Science Education and Research, Kolkata Title: Topological Photo-current and magnetization control in 3D Topological Insulators Location: In-Person Presentation, CDP Show/Hide Abstract Optical control of helicity-dependent photocurrent has also been studied in 3D topological insulators. Strong spin-orbit coupling and spin-momentum locking make this system unique for their applications. We observed that photocurrent can be controlled by exciting the sample with different circular and linear polarized light, yielding a polarization-dependent current density which can be fitted very well with a theoretical model. This photocurrent
can also be controlled with the help of photo-thermal gradient generated by the excitation light beam.
Enhancement and inversion of this photocurrent in presence of photo-thermal gradient for light incident on two opposite edges of the sample occur due to selective spin state excitation with two opposite (left and right) circularly polarized light in presence of the unique spin-momentum locked surface states.
We also present efficient spin to charge conversion (SCC) in the topological insulator and ferromagnetic thin films based heterostructure by using spin-pumping technique The SCC, characterized by inverse Edelstein effect length (kIEE) in the TI material, gets altered with an intervening Copper (Cu) layer, and it depends on the interlayer thickness. The introduction of Cu layer at the interface of TI and FM metal provides a new degree of freedom for tuning the SCC efficiency of the topological surface states. The significant enhancement of the measured spin-pumping voltage and the increased linewidth of ferromagnetic resonance absorption spectra due to the insertion of Cu layer at the interface indicate a reduction in spin memory loss at the interface that resulted from the presence of exchange coupling between the surface states of TI and the local moments of FM metal.
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Abstract Number: ANPA2024-N00038 Presenting Author: Deergh Bahadur Shahi Presenter's Affiliation: Patan Multiple Campus, Patandhoka, Lalitpur, Tribhuvan University, Nepal Title: Thickness Dependent Electronic Properties and Cleavage energy of Pt2HgSe3 Location: In-Person Presentation, CDP Show/Hide Abstract The size and thickness limitations of synthesized Jacutingaite (Pt2HgSe3) make it difficult to study its quantum properties, such as its dual-topological nature and large-gap quantum spin Hall state, through a layer-controlled mechanism. Although theoretical calculations have explored these properties in monolayers, experimental studies have been hindered by the challenges associated with size and layer number limitations during exfoliation. To investigate the quantum properties of Jacutingaite, we use a combination of mechanical exfoliation and plasma-assisted thinning to obtain very few layers, and potentially mono- or bilayers. Our goal is to study the electronic properties of layer-controlled (mono to few layer) Jacutingaite by fabricating quantum Hall devices and conducting ARPES studies. We additionally perform density functional theory calculation to study the electronic properties and the cleavage energy of mono to few layer by using the full-potential local-orbital code. The cleavage energy of mono, bi and tri-layers are found to be within 0.46-0.54 Jm-2 which is closely comparable with graphite. Metal-insulator-transition are observed with increase in thickness.
This work is supported by the Brain Pool program (No. RS-2023-00304344), National Research Foundation of Korea and University Grants Commission (CRG-78/79 S&T-03), Nepal.
Keywords: Jacutingaite, mechanical exfoliation and plasma-assisted thinning, Density functional theory, Cleavage energy, Topological phase transition
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Abstract Number: ANPA2024-N00039 Presenting Author: Dipak Bhattarai Presenter's Affiliation: PhD scholar, Institute of Science and Technology, Tribhuvan University, Nepal Title: Electronic Structure and Anomalous Hall Conductivity of Magnetic Weyl Ferromagnet Bi2TeMnI2 Location: In-Person Presentation, CDP Show/Hide Abstract Electronic Structure and Anomalous Hall Conductivity of Magnetic Weyl Ferromagnet Bi2TeMnI2
Dipak Bhattarai1, and Madhav Prasad Ghimire1,2
1 Central Department of Physics, Tribhuvan University, Kirtipur, 44613, Kathmandu, Nepal
2 Leibniz - IFW Dresden, Helmholtzstr-20, 01069 Dresden, Germany
Email: dipak.bhattarai@trc.tu.edu.np
Abstract:
Weyl semimetals (WSM) represent a category of crystalline materials distinguished by their exceptional electronic characteristics, defined by the existence of Weyl fermions [1]. They are intriguing for electronics and spintronics due to their unique band structure with Weyl points, leading to exotic phenomena such as chiral anomaly and Fermi arcs [2]. In search for new WSM, we consider magnetic doping (i.e., Mn) to the Te site of BiTeI. For this calculations, we use full-potential local orbital (FPLO) code [3] which is based on density functional theory. Our calculations for the parent compound BiTeI is nonmagnetic while the Mn substituted to the Te-site (i.e., Bi2TeMnI2) suggest a ferromagnetic ground state in optimized state with an effective magnetic moment of 3.41 μB per unit cell. Magnetic doping transforms BiTeI from narrow band gap semiconductor to a ferromagnetic WSM due to change in the electronic band topology. Our study confirms that Bi2TeMnI2 has 6 Weyl points around 100 meV above the Fermi level. The calculated intrinsic anomalous Hall conductivity is ~575 (Ω-cm)-1. Based on our calculations, we predict the Bi2TeMnI2 to be a promising candidate for high-speed electronics and spintronics device.
This work is supported by grants from TWAS-UNESCO (21-377 RG/PHYS/AS_G), Italy and University Grants Commission (CRG-78/79 S&T-03), Nepal. D.B. acknowledges the Nepal Academy of Science and Technology, Khumaltar, Nepal for PhD fellowship and Department of Science and Technology, Government of India for ISRF-2022 award.
References
1. X. Wan, A. M. Turner, A. Vishwanath, and S. Y. Savrasov, Phys. Rev. B 83, 205101 (2011).
2. Huang et al. Phys. Rev. X 5, 031023 (2015).
3. K. Koepernik, and H. Eschrig, Phys. Rev. B 59, 1743 (1999).
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Abstract Number: ANPA2024-N00040 Presenting Author: Mithilesh Kumar Jha Presenter's Affiliation: Ph.D Scholar, Central Department of Physics, TU, Kirtipur, Kathamndu, Nepal Title: Computational Study on Electrical Properties of NiPtCu Solid Ternary Alloy Location: In-Person Presentation, CDP Show/Hide Abstract Alloying is one of the commonly used tool in order to explore the new properties of elements. We generally explore six different types of properties of any material viz. - mechanical, thermal, optical, electrical, magnetic and chemical properties. The properties of materials may vary with shape and size. The materials in bulk shows one type of property whereas in nano-particle or films it may show different properties. In this study, we are focused on exploring the electrical properties of solid ternary alloy NiPtCu2. We used Quantum Espresso, a freeware to investigate the electrical properties. We designed the solid ternary alloy in bulk form and calculated the cut off energy, pseudopotential, brillouin zone, density of state (DOS) and band structure of the considered molecules. The detailed results of this solid ternary alloy will be comprehensibly presented.
Key words: Solid ternary alloy, bulk form, pseudopotential, brillouin zone and band structure.
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Abstract Number: ANPA2024-N00041 Presenting Author: Sarita Lawaju Presenter's Affiliation: Central Department of Physics, Tribhuvan University Title: Layered Honeycomb Oxides: Possible Candidates for Energy Storage Location: In-Person Presentation, CDP Show/Hide Abstract Honeycomb layered compounds are structures having different hexagonal arrays forming the honeycomb layers. This study focused on the mixed metal honeycomb oxides of type A3MM’BO6 [A = Na, Li, Cu; M = transition metals, M’ = Mg, Cu, Zn; B = Bi, Sb, Ru] which are also known as rock-salt superstructures and are extensively studied for their structure, magnetic, electrochemical, photocatalytical, quantum properties, etc. The oxides Na3NiMgSbO6 and Na3NiZnSbO6 have been synthesized by high temperature solid state reactions. Field emission scanning electron microscopy (FESEM), energy dispersive spectrometry (EDS), powder X-ray diffraction (PXRD) followed by Rietveld refinements and Raman measurements were carried out to study their surface morphology and structural properties. The surface morphology showed the homogeneous crystallites formation whereas EDS confirmed the ratio of Ni, Mg/Zn, Sb to be 1:1:1. The structural refinements of PXRD patterns of these oxides revealed their monoclinic symmetry [Space Group: C2/m (12)]. These oxides have quasi two-dimensional Na+ ions in the interlayer region separated by the honeycomb layers (NiMgSbO6)3- and (NiZnSbO6)3- formed in ordering of the atoms in above mentioned ratio (1:1:1). The Raman peaks further support the formation of oxides and presence of respective metal-oxide bonds and hence successful synthesis of these oxides. The lattice information obtained from the structural refinements were carried out for further density functional calculations to study their electronic and magnetic properties. The scope of this ongoing work is to explore the potential application of honeycomb layered oxides as energy-storage devices.
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Abstract Number: ANPA2024-N00058 Presenting Author: Binod K Rai (Invited) Presenter's Affiliation: Savannah River National Laboratory Title: Binary Actinide Oxides: Synthesis, Crystal Structures, and Magnetic Properties Location: Virtual Presentation Show/Hide Abstract Actinides, with their distinctive electronic configurations, play a crucial role in the advancement of quantum phenomena research and the nuclear industry, promising significant technological advancements. These elements exhibit the dual nature of 5f-states, competing interactions, and strong spin-orbit coupling, leading to complex magnetic behaviors such as multi-k antiferromagnetic ordering, multipolar ordering, and mixed valence configurations. The structural and magnetic properties of actinide systems are a focal point due to their intriguing nature. Despite the allure of their properties, research has been limited by their toxicity, radioactivity, and high reactivity. Traditionally, studies on actinide oxides have primarily focused on uranium and plutonium compounds within nuclear fuel contexts. However, the physical properties of other actinide oxides remain underexplored. This presentation will cover the synthesis methods for selected binary actinide oxides, including dioxides and sesquioxides, and provide insights into their current understanding of crystal structures. Additionally, the talk will address the challenges in unraveling the magnetic properties of these oxides, aiming to foster a deeper comprehension of their complex phenomena.
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Abstract Number: ANPA2024-N00059 Presenting Author: Milo Xavier Sprague Presenter's Affiliation: University of Central Florida Title: Absence of Electronic Structure Reconfiguration in EuSnP Across the Antiferromagnetic Transition Location: Virtual Presentation Show/Hide Abstract Magnetic ordering in lanthanide-based metals is commonly attributed to RKKY interactions, where localized magnetic f electrons interact magnetically with itinerant conduction electrons through exchange interactions. Due to the intricate interplay between the electronic band structure and magnetic ordering, many lanthanide magnetic metals undergo significant changes in their electronic spectrum. In our study of the europium-based antiferromagnetic metal EuSnP, employing angle-resolved photoemission spectroscopy (ARPES) and first-principles density functional theory (DFT) calculations, we surprisingly found no modifications to the band structure upon cooling below the paramagnetic to antiferromagnetic transition temperature. We discuss potential reasons for this absence of observed reconstruction in this compound.
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Abstract Number: ANPA2024-N00060 Presenting Author: Nathan Valadez Presenter's Affiliation: University of Central Florida Title: Momentum Dependent Charge Density Wave Gap in an Antiferromagnetic Metal Location: Virtual Presentation Show/Hide Abstract Charge density wave (CDW) ordering has been an important topic of study for a long time owing to its connection with other exotic phases such as superconductivity and magnetism. The RTe3 (R = rare-earth elements) family of materials provides a fertile ground to study the dynamics of CDW in van der Waals layered materials, and the presence of magnetism in these materials allows to explore the interplay among CDW and long range magnetic ordering. Here, we have carried out a high-resolution angle-resolved photoemission spectroscopy (ARPES) study of a CDW material GdTe3, which is antiferromagnetic below ∼ 12 K, along with thermodynamic, electrical transport, magnetic, and Raman measurements. Our ARPES data show a two-fold symmetric Fermi surface with both gapped and ungapped regions indicative of the partial nesting. The gap is momentum dependent, maximum along Γ−Z and gradually decreases going towards Γ−X. Our study provides a platform to study the dynamics of CDW and its interaction with other physical orders in two- and three-dimensions.
*This work is supported by the National Science Foundation under CAREER award DMR-1847962, the NSF Partnerships for Research and Education in Materials Grant DMR-2121953, and the Air Force Office of Scientific Research MURI Grant No. FA9550-20-1-0322.
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Abstract Number: ANPA2024-N00061 Presenting Author: Iftakhar Bin Elius Presenter's Affiliation: University of Central Florida (UCF) Title: Electronic Structure of a Nodal Line Semimetal Candidate Location: Virtual Presentation Show/Hide Abstract LnSbTe (Ln= lanthanides) compounds isostructural to well-known ZrSiS family of nodal line semimetals offer a rich platform for studying topological features as well as interaction of topology, magnetism, and electronic correlation owing to the presence of 4f electrons. We performed systematic magnetic field induced thermal transport, temperature dependent magnetic susceptibility and field dependent magnetization studies of rare-earth based ternary semimetals of this series at low temperature. To investigate the electronic structure of the materials, angle resolved photoemission spectroscopy (ARPES) and first principles-based calculations were performed. Multiple nodal lines along Γ−X and Γ−M high symmetry directions were observed in photon energy dependent ARPES measurements. Our investigation indicates that this system can provide a rich platform to study the interplay of magnetism, topology and correlation.
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Abstract Number: ANPA2024-N00062 Presenting Author: Tej Nath Lamichhane Presenter's Affiliation: University of Central Oklahoma Title: Technological application of novel magnetic materials Location: Virtual Presentation Show/Hide Abstract Magnetic materials are dominant foundations for versatile technological applications all in bulk, micro/nanomaterials, and thin interfaces forms. Bulk magnetic materials are workhorses for design of large electrical machines whereas nanomaterials and interfaces dominate in sensing, data recording, storage, image, and information processing. This presentation will broadly review all the latest booming technological frontiers of novel magnetic materials. At the end, a little more details of the biological applications of magnetic nanoparticles and interfaces will be discussed.
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Abstract Number: ANPA2024-N00063 Presenting Author: Mohamed El Gazzah Presenter's Affiliation: University of Notre Dame Title: Doping-induced spin reorientation in TmMn6Sn6 Location: Virtual Presentation Show/Hide Abstract The kagome-lattice compounds RMn6Sn6 (R is a rare earth element), where the Mn atoms form a kagome net in the basal plane, are currently attracting a great deal of attention as they've been shown to host complex magnetic textures and electronic topological states strongly sensitive to the choice of the R atom. Among the magnetic R atoms, TmMn6Sn6 orders with the easy-plane magnetization forming a complex magnetic spiral along the c-axis. Previous neutron studies carried on polycrystalline samples have shown that Ga doping changes the magnetic anisotropy from easy-plane to easy-axis. Here we present magnetic and magnetotransport measurements on a single crystal and first principles calculations in the doping series TmMn6Sn6-xGax. We find that the magnetic properties are highly sensitive even to a small concentration of Ga. At small Ga concentrations, the in-plane anisotropy is maintained, which gradually changes to the out-of-plane anisotropy with increasing Ga. We will discuss these observations with respect to the effect of modification of the Tm crystal field, introduced by Ga doping.
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Abstract Number: ANPA2024-N00064 Presenting Author: Resham B Regmi Presenter's Affiliation: University of Notre Dame Title: Collinear Altermagnetism in layered intercalated transition metal dichalcogenide compound CoNb4Se8 Location: Virtual Presentation Show/Hide Abstract Other than conventional classes of magnetic states Ferromagnets (FM) and Antiferromagnets (AF), Altermagnets (AM) are now proved to be a distinct third magnetic state in condensed matter physics. AM’s are catching attention due to its potential application in future spintronic devices. AM’s have alternating spin polarization in reciprocal space electronic band structure like in FM’s even without spin orbit coupling and also possesses zero-net magnetization like in AF, both of these properties in overall can contribute to ultrafast dynamics. So far, altermagnetic materials have been experimentally identified only in handful of materials like semiconducting MnTe and also in metallic CrSb but both of these materials possess various difficulty such as single crystal synthesis with single phase and sample dependent properties in MnTe while CrSb has small crystal sizes that limits magnetic and transport as well as other measurement in a particular orientation in ab-pane. Hence, We have grown single crystals of easily growable altermagnetic candidate material in layered CoNb4Se8 which belongs to a popular class of intercalated transition metal dichalcogenide family of 2H-NbSe2 compounds in a hexagonal space group P63/mmc and studied magnetic and transport properties on this compound. The altermagnetic transition temperature is observed consistently in magnetic susceptibility, electronic transport and thermal measurement at 168 K. In addition, the A-type antiferromagnetic ordering on this compound is verified by single crystal neutron diffraction confirming the easy axis magnetic moments are colinearly aligned along the c-axis.
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Abstract Number: ANPA2024-N00065 Presenting Author: Jittin V Thoms Presenter's Affiliation: Department of Physical and Applied Sciences, University of Houston-Clear Lake, Houston, TX, 77058, USA Title: Surface Plasmons-Enhanced Photoresponsivity in Au Nanoparticles/2D Bi2O2Se Hybrid Material Location: Virtual Presentation Show/Hide Abstract Zipper two-dimensional (2D) materials such as Bi2O2Se have emerged as promising alternatives to van der Waals 2D materials for high-performance optoelectronic applications. However, the relatively low bandgap (~1.5 eV) of Bi2O2Se limits its photodetection capability to the near-infrared (IR) region. In this study, we report enhanced photoconductivity and photoresponsivity in a micro-sized photodetection device fabricated using a hybrid material composed of Bi2O2Se nanosheets and gold (Au) nanoparticles, under visible light illumination. The electrical conductivity of the Au nanoparticles/Bi2O2Se film in the photodetection device was measured to be ~1x10-3 S/m, an order of magnitude higher than that of the pure Bi2O2Se film. The device made with the Bi2O2Se film exhibited a photoresponsivity of ~2 x10-4 A/W under green and red laser illumination, which increased by roughly three times to ~7 x10-4 A/W for the device fabricated with the Au nanoparticles/Bi2O2Se hybrid material. This enhancement in photoresponsivity is attributed to the excitation of surface plasmons on Au nanoparticles and the increased number of photons interacting with the material. By optimizing the material and device design, this approach paves the way for developing cost-effective and efficient photodetection devices for future applications.
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Abstract Number: ANPA2024-N00066 Presenting Author: Gabriel Kinney Presenter's Affiliation: Cumberland International Early College High School, Fayetteville, NC 28301, USA Title: Crystallography and DFT investigation on Sc2C MXene Location: Virtual Presentation Show/Hide Abstract Sc2C is an example of two-dimensional MXenes composed of layered scandium and carbon atoms. Sc2C crystallizes to trigonal crystal structure with its atoms arranged in a hexagonal lattice system. We aim to investigate Sc2C by looking at its electronic structure, magnetism, and optical properties. We optimize the crystal structure minimizing the energy and force using the Vienna Ab initio Simulation Package (VASP). The optimized structure is then used to calculate the material’s power diffraction pattern, density of state, bandgap, and magnetism. We use Visualization for Electronic Structural Analysis (VESTA) for crystallographic analysis. Sc2C MXene is a metallic nonmagnetic inorganic compound. It has high electrical conductivity, excellent thermal conductivity, larger surface to volume ratio, and exceptional mechanical strength as needed in the advancement of current technology.
This work is supported by the Department of Energy BES-RENEW award number DE-SC0024611.
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Abstract Number: ANPA2024-N00067 Presenting Author: Yamuna Paudel Presenter's Affiliation: CUNY Advanced Science Research Center Title: Semiconductor Metasurfaces for the Enhancement of Photocatalytic and Photovoltaic Activity Location: Virtual Presentation Show/Hide Abstract Solar energy is a continuous renewable source of energy. Utilization of the enormous amount of available solar energy as a clean alternative to fossil fuels is extremely important. Besides the most common application of solar cells to produce electricity, there is also potential to use solar energy for hydrogen gas production and industrial waste utilization such as methane and carbon reduction. Although extensive research has been reported in these fields, only a limited fraction of the total energy from the sun can currently be used due to the limitations of today’s technology. To this end, a question emerges: Are there appropriate ways to utilize the energy from the Sun more effectively and therefore develop more efficient solar harvesting devices with suitable earth-abundant materials? We propose to use Gallium Arsenide (GaAs) and amorphous Silicon (a-Si) semiconductors to create a patterned surface of periodic nanostructures, known as a metasurface, to enhance absorption to near unity in the visible light regime. Our project covers the design and fabrication of these ultrathin ( 150 nm height) periodic structures, which due to the electromagnetic field localizations and interferences from the Mie Resonance modes, exhibit simultaneous suppression of almost all reflection and transmission. Recently, we have minimized the optical reflectivity (< 10 %) using our method and are optimizing the surface properties, DC conductivity, and carrier dynamics of the nanostructures that already greatly surpasses a flat film by all metrics mentioned above. Finally, we will use the solar energy captured by these metasurfaces for photovoltaic applications, hydrogen production via water splitting, and other electrochemical processes.
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Abstract Number: ANPA2024-N00068 Presenting Author: Saniya L. Lyles Presenter's Affiliation: Department of Chemistry, Physics and Materials Science, Fayetteville State University, Fayetteville, NC 28301, USA Title: Crystallography and DFT investigation on Ti2C MXene Location: Virtual Presentation Show/Hide Abstract MXenes are layered inorganic compounds of early transition metal carbide or nitride or carbonitride nanomaterials synthesized from their MAX phases by selective chemical etching of atomic A-layers binding the quasi-two-dimensional M-X layers. In this study, we analyze the crystal structure and carry out the first-principle density functional theory calculations on Ti2AlC MAX phase and Ti2C Mxene. Ti₂AlC crystallizes to a hexagonal crystal with P6₃/mmc space group (space group # 194). Each Ti atom is bonded to three equivalent Al and three equivalent C atoms with Ti-Al bonds slightly larger than Ti-C bonds. C is bonded to six equivalent Ti atoms to form CTi₆ octahedra. Ti₂C crystallizes in the cubic Fd̅3m (# 227) space group. Each Ti is bonded to three equivalent C atoms whereas each C atom is bonded to six equivalent Ti atoms to form edge-sharing CTi₆ octahedra. Ti2C has strong light absorption in visible wavelengths. Ti₂C has zero band gap and zero magnetic moment.
This work is supported by the Department of Energy BES-RENEW award number DE-SC0024611.
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Abstract Number: ANPA2024-N00069 Presenting Author: Christopher Kai Addaman Presenter's Affiliation: Department of Chemistry, Physics and Materials Science, Fayetteville State University, Fayetteville, NC 28301, USA; Cross Creek Early College High School, Fayetteville, NC 28301, USA Title: Electromagnetic Structure and Crystallography of Ti2N MXene from DFT Calculations Location: Virtual Presentation Show/Hide Abstract MXenes are a class of two-dimensional inorganic compounds known for their higher conductance and excellent mechanical properties with larger surface-to-volume ratio. They consist of thin layers of transition metal carbide, nitride, or carbonitride, which are able to exist as a single layer nanosheet. They have the ability to bond with a diverse set of hydrophilic terminations such as -F, -O, -OH, and -H. In this study, we have observed the properties of pristine Ti2N MXene by analyzing simulated powder diffraction patterns, band structures, crystalline structures, their density of state, and optical properties. Using the Vienna Ab initio Simulation Package (VASP), we simulated the structure of Ti2N to find the most stable crystal structure for a chosen symmetry. We used the optimized structure to analyze electronic structure, magnetism, and optical properties of Ti2N. Additionally, we utilized the Visualization for Electronic and Structural Analysis (VESTA) tool to analyze the crystallography of Ti2N. Calculations show Ti2N is a non-magnetic, metallic compound.
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Abstract Number: ANPA2024-N00070 Presenting Author: Talon David Alexander Presenter's Affiliation: Department of Chemistry, Physics and Materials Science, Fayetteville State University, Fayetteville, NC 28301, USA; Cross Creek Early College High School, Fayetteville, NC 28301, USA Title: Crystallography, Electronic Structure, and Magnetism of Ti3N2 MXene from DFT Calculations Location: Virtual Presentation Show/Hide Abstract Ti3N2 is a transition metal nitride that is part of a group of two-dimensional inorganic compounds known as MXenes. MXenes’ interesting electrochemical properties offer a wide variety of applications within electronic devices such as ion battery electrodes. We perform the first-principle density functional theory calculations using the Vienna Ab initio Simulation Package known as VASP to optimize the crystal structure and analyze the band structure, density of states, magnetism, and optical properties of Ti3N2. The optimized structure was then studied with the aid of the Visualization for Electronic and STructural Analysis package known as VESTA. The calculation shows that the monolayer of Ti3N2 is a ferromagnetic half-metallic compound with zero band gap, but anti-ferromagnetic in the three-dimensional bulk structure.
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Abstract Number: ANPA2024-N00071 Presenting Author: Laxmi khatiwada Presenter's Affiliation: Tribhuvan University Title: ADVANCED SOLID-STATE BATTERIES WITH INNOVATIVE SOLID ELECTROLYTE FABRICATION TECHNIQUES SHADING LIGHTS ON ENERGY DENSITY AND CYCLIC DURABILITY TESTING Location: Virtual Presentation Show/Hide Abstract Solid-state batteries are advanced ones which ensure higher energy storage devices, providing significant development in energy density, safety and longevity than that of traditional lithium ion batteries. This paper explores the technique of fabrications of solid state batteries followed by the performance which particularly gives knowledge about energy density and cyclic durability. This includes manufacturing processes which aims to optimize the size of electrolytes and electrodes with minimizing internal resistance. Cyclic durability testing and energy density calculation was carried out to observe the performance of advanced solid state technology. The solid-state batteries represent an energy density of approximately 300Wh/kg, which is a great improvement over conventional lithium-ion batteries. Cyclic durability test showed 200 charge-discharge cycles, which retained 86.67% of initial capacity with a degradation rate of 0.0667% per cycle that showed higher energy densities by maintaining suitable cyclic durability. This study provides detailed information about the importance of material innovation which also paves the way for electric vehicles, portable electronics and large -scale energy storage systems. Provide directions for continuous exploration of new materials which are eco-friendly which can improve the performance of solid state batteries.
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Abstract Number: ANPA2024-N00072 Presenting Author: Poojan Koirala Presenter's Affiliation: Tribhuvan University Title: Tuning the electronic band gap of Bi(2)Y(1-x)Zr(x)O(4)Cl: A density functional calculations Location: Virtual Presentation Show/Hide Abstract Bismuth oxyhalide, a promising photocatalyst material, has been extensively studied in recent years. Because of its high photocatalytic efficiency, it can play significant role in minimizing energy crisis and environmental related problems. In order to boost the solar energy conversion of bismuth oxyhalides, there exists several methods of tuning their band structures through chemical doping, heterojunction construction, strain modulation and so on. We perform density functional theory (DFT) calculations using full-potential local-orbital (FPLO) code. The standard GGA and GGA+mBJ functionals have been used in our calculations. We consider chemical doping, in particular, electron doping (i.e., Zr) in Bi2YO4Cl at the Y site via virtual crystal approximation. With upto 30% doping, the structural property is found to hold stable crystal structure similar to the parent Bi2YO4Cl. The parent compound Bi2YO4Cl was found to be an indirect band gap semiconductor with around 2.4 eV band gap. Upon 30% doping, the band gap decreases to 2.3 eV. The major contributions to the valence region are from oxygen-2p orbitals hybridizing with the Cl-3p orbitals whereas the conduction region are dominated by Bi-6p orbitals. Except the band gap, no significant changes are observed in doping. The calculated values of band gap are found to agree with our experimental measurement.
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Abstract Number: ANPA2024-N00073 Presenting Author: Sudhan Koirala Presenter's Affiliation: Tribhuvan University, Nepal Title: Photocatalytic Dye Degradation & Antimicrobial Activity of Bi2WO6/ZnO Nanocomposite Location: Virtual Presentation Show/Hide Abstract This study focuses on the degradation of various dyes using visible light-driven heterogeneous semiconductor photocatalysis. Bi2WO6/ZnO Binary composite material was synthesized via a hydrothermal method and characterized using various analytical techniques, revealing enhanced visible light photosensitivity attributed to a reduced band gap. The photocatalytic efficiency of Bi2WO6/ZnO was evaluated by degrading cationic and anionic dyes under visible light exposure for 90 min. Kinetic studies demonstrated high degradation efficiencies for cationic dyes, with 99.94% degradation of RhB, 96% degradation of MB, 88% degradation of CV, and 66% degradation but MG removal within 30 min, while anionic dyes showed slightly lower degradation percentages. Additionally, the Bi2WO6/ZnO composite exhibited significant antimicrobial activity against various microorganisms, including Escherichia coli, Staphylococcus aureus, and Candida albicans. This research highlights the potential of Bi2WO6/ZnO composites for efficient photodegradation of organic pollutants and underscores their promising antimicrobial properties under visible light irradiation.
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Abstract Number: ANPA2024-N00074 Presenting Author: Karan Giri Presenter's Affiliation: a. National Yang Ming Chiao Tung University, Taiwan, b. Tri-Chandra Multiple Campus, Tribhuvan University, Nepal Title: Enhanced thermoelectric transport characteristics of novel BiSbTe-WSe2 composite films Location: Virtual Presentation Show/Hide Abstract A novel approach has been devised to integrate two distinct layered materials, bismuth antimony telluride (BiSbTe) and tungsten diselenide (WSe₂), both renowned for their efficiency in waste heat recovery and exceptionally low thermal conductivity, respectively. To further enhance thermoelectric properties, WSe₂ is periodically encapsulated within the primary target Bi₁.₅Sb₀.₅Te₃ using a pulsed laser deposition technique. This study marks the first instance where WSe₂ is co-ablated with BiSbTe at four different deposition temperatures, producing hetero-nanocomposite thin films. Various characterization techniques were employed to determine the thermoelectric properties. Both x-ray diffraction (XRD) and Raman spectroscopy confirm the presence of BST and WSe₂ as distinct phases. The electrical transport properties significantly improved due to optimized hole concentration, resulting in very high electrical conductivity, ranging from hundreds to thousands of S cm⁻¹ for samples grown at 573 K and 723 K, respectively. Furthermore, Seebeck coefficient measurements showed highly optimized values, indicating a satisfactory balance between thermoelectric parameters. This resulted in a substantial increase in the power factor, calculated as high as 150 μW cm⁻¹ K⁻², demonstrating excellent thermoelectric performance. The enhanced thermoelectric transport properties of WSe₂ periodically encapsulated in the BiSbTe matrix position it among the top thermoelectric materials with excellent performance for solid-state refrigeration and power generation applications.
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Abstract Number: ANPA2024-N00075 Presenting Author: Laxman Chaudhary Presenter's Affiliation: AMRL, Central Department of Physics TU, Nepal. Title: Effects of Electron Doping in Electronic structure and Fermi Surface Morphology of HfTe2 Location: Virtual Presentation Show/Hide Abstract The electronic structure and Fermi surface morphology of Hf1-xTaxTe2 has been explored by means of density functional theory approach. We consider electron doping by using virtual-crystal approximation implemented in full-potential local-orbital (FPLO) code. We note that with increase in doping concentration, the density of states shifts from valence region towards the conduction region. Specifically, Hf-5d orbitals are found to accumulate near the Fermi level, while Te-5p contributions remain relatively unchanged. For a doping concentration ranging above 10%, the system transforms to metallic state with strong hybridization between the dopant and host states. The Fermi-surface provides a visual insights into the doping-induced distortions, revealing a gradual decrease in the size of the Dirac cone and associated sphere, accompanied by a reduction in the hole pocket at the Γ-point. As doping increase beyond 20%, an increase in electron populations and further distortions are observed in the Fermi surface. The Dirac cone shrinks further, and at 25% doping, a crucial transition occurs: a gap opens between the linearly touching bands at the Dirac points (Z-point) in the Brillouin zone, signifying a distinct change in the electronic
landscape. The observed changes offer valuable insights into the material's potential for manipulation and control of its electronic properties, paving the way for the design of electronic devices.
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Abstract Number: ANPA2024-N00076 Presenting Author: Bhupendra Sharma Presenter's Affiliation: Central Department of Physics, Tribhuvan University Title: Structural Stability and Electronic Structure of Monolayer Mo0.5W0.5Te2 Location: Virtual Presentation Show/Hide Abstract The monolayers of MoTe2 and WTe2 provide a rich atomically thin platform to explore topological physics, electrically switchable circular photogalvanic effect, rectification, and quantum nonlinear Hall effects. For realization of the nonlinear quantum phenomena, a nonzero Berry-curvature dipole (BCD) is required, which has been demonstrated in pristine WTe2 and MoTe2 monolayers recently. In this work, we theoretically design a new monolayer Mo0.5W0.5Te2 using the pristine Td-WTe2 and systematically substituting Mo in W site of Td-WTe2. By means of density functional theory approach, we explored the structural stability and electronic structure of Mo0.5W0.5Te2. We confirm the dynamical stability of Mo0.5W0.5Te2 monolayer with phonon band structure and density of states. Our electronic band structure calculations reveal the presence of a relatively much smaller bandgap near the Fermi level compared to that of the pristine Td-WTe2 and Td-MoTe2 monolayers. Such a narrow bandgap can lead to divergence of Berry curvature near the Fermi level yielding a large enhancement of BCD. In fact, our preliminary results shows significant enhancement of BCD in Mo0.5W0.5Te2 monolayer.
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Abstract Number: ANPA2024-N00077 Presenting Author: Prakash Khatri Presenter's Affiliation: Central Department of Physics, Tribhuvan University Title: Mechanical and Thermoelectric Behavior of 18-Valence Electron Half Heusler Tellurides XFeTe (X=Ti, Hf): A Theoretical Insight Location: Virtual Presentation Show/Hide Abstract Mechanical and Thermoelectric Behavior of 18-Valence Electron Half Heusler Tellurides XFeTe (X=Ti, Hf): A Theoretical Insight
Prakash Khatri 1, 2, N. P. Adhikari 1,*
1Central Department of Physics, Tribhuvan University, Kirtipur 44613, Kathmandu, Nepal
2Department of Physics, Tribhuvan University, Siddhanath Science Campus, Mahendranagar 10406, Nepal
Corresponding Email*: narayan.adhikari@cdp.tu.edu.np
Abstract
Half Heusler (hH) compounds offer a cost-effective and efficient solution for addressing the growing global energy needs in power generation applications. The present examines the structural, electronic, magnetic, lattice dynamics, mechanical, and thermoelectric (TE) properties of two novel hH tellurides, XFeTe ( X = Ti, Hf). We utilize Density Functional Theory (DFT), Semi-classical Boltzmann Transport Equations (BTE), Quasi-harmonic Approximation (QHA), Density Functional Perturbation Theory (DFPT), and Deformation Potential Theory (DPT) in our investigation. Both compounds exhibit nonmagnetic semiconductor properties, with each having an indirect band gap of 0.93 eV and 0.79 eV, for X=Ti and Hf respectively. Both compounds demonstrate dynamical and mechanical stability. TiFeTe exhibits ductility, while HfFeTe is brittle. Elastic constants analysis indicates that these compounds possess stiffness, enhanced hardness, elastic anisotropy, and high melting points. The electrons in TiFeTe and HfFeTe demonstrate remarkably low effective masses of 0.72me and 0.61me, respectively, at the conduction band minima leading to prolonged relaxation times. Using temperature-dependent relaxation time, the maximum zT values for the n-type and p-type compositions are 1.79 and 1.11 for TiFeTe, and 1.35 and 1.06 for HfFeTe, respectively, at 1200 K. The n-type composition performs better than the p-type and reaches peak zT at more practicably feasible doping levels.
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Abstract Number: ANPA2024-N00078 Presenting Author: Pankaj Singh Dhami Presenter's Affiliation: Central Department of Physics, Tribhuvan University, Kathmandu, Nepal Title: Synthesis and Characterization of Fe@Cu Bimetallic Nanoparticles: Microemulsion Technique Location: Virtual Presentation Show/Hide Abstract The primary objective of this study is to synthesize Fe@Cu bimetallic nanoparticles using microemulsion techniques. Microemulsion techniques are widely employed for the controlled fabrication of nanoparticles with specific shapes and dimensions. The synthesized nanoparticles were characterized through UV-VIS spectroscopy, Fourier Transform Infrared spectroscopy (FTIR), and X-ray diffraction (XRD). X-Ray Diffraction (XRD) analysis revealed that the crystallite sizes of the Fe@Cu bimetallic nanoparticles fell within the range of 14.52 nm. The XRD graph also indicated the presence of copper peaks at 2θ values of 34.520, 42.60, 50.60, and 74.10, as well as iron peaks at 43.70. Additionally, we observed several oxide peaks for both copper and iron particles at 24.50, 29.20, 30.00, 31.40, 33.10, 37.00, and 61.80, suggesting that a minor portion of copper had undergone oxidation and transformed into copper oxide. Peaks at 65.10 and 83.00 indicated the presence of iron oxide. UV-VIS spectroscopy of the Fe@Cu bimetallic nanoparticles exhibited a maximum peak at (312± 8.20) nm, with direct and indirect band gap energies of (2.52± 0.20) eV and (2.20± 0.02) eV, respectively. Both the indirect and direct band gaps demonstrated semiconductor behavior. Furthermore, UV-VIS spectroscopy revealed the surface plasmon resonance of Cu nanoparticles at (459± 1.13) nm. Fourier-transform infrared spectroscopy of Fe@Cu bimetallic nanoparticles identified peaks at 680.87 cm-1 and 607.57 cm-1, confirming the presence of Cu-O bonds, which align with Fe in the core and Cu on the shell. Moreover, this study included the preparation of Cu@Fe bimetallic nanoparticles, as well as monometallic copper (Cu) and iron (Fe) nanoparticles. The characterization of these materials involved UV-VIS spectroscopy and FTIR spectroscopy.
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Abstract Number: ANPA2024-N00079 Presenting Author: Krishna Bahadur Rai Presenter's Affiliation: Central Department of Physics, TU Title: First-Principles DFT Study of the Equilibrium Configuration, Electronic Structures, Vibrational Analysis and Thermodynamic Properties of Anisole and Chlorine Substituted Anisole Location: Virtual Presentation Show/Hide Abstract Anisole is an organic molecule that synthesizes various aromatic chemicals, pharmaceuticals, dyes, solvents, and fragrances. The study investigates the structural, electronic, vibrational, and thermodynamic properties of anisole and chlorine-substituted derivatives, namely ortho-chloroanisole (OCA), meta-chloroanisole (MCA), and para-chloroanisole (PCA) using the DFT/B3LYP method and 6-31+G(d,p) basis set. Employing this consistently yields minimal optimal energy for MCA equal to -21,943.04 eV which is found to be the most stable molecule among others. Molecular electrostatic potential mapping indicates higher reactivity in chlorine-substituted anisoles, identifying key reactive sites such as oxygen, chlorine, and carbon. Frontier Molecular Orbitals interpret anisole as having an excitation energy of 5.770 eV referring to kinetically stable and PCA having an energy gap of 5.481 eV indicating a less stable and more kinetically reactive molecule. Global reactivity parameters generally comment on reactive properties and address the PCA with a low value of chemical hardness 2.7405 eV is the lowest stable and anisole is most stable with less electronegativity of 3.28505 eV. The energy gaps observed in the Density of state (DOS) spectrum and FMOs are equivalent and correspond well with each other. Non-Covalent Interactions (NCI)-Reduced Density Gradient (RDG) demonstrates weak H-bonding and strong repulsive interactions. Positive Mulliken atomic charges on Carbon and Chlorine atoms and negative Mulliken charges on Oxygen atoms due to their electronegative and electron-withdrawing nature have been observed. Vibrational frequencies for C-H, C-O, and C-Cl vibrations with IR and Raman spectra are well observed between the frequency ranges of 0-4000 cm-1. In the UV-visible spectra, the spectral intensity of all the molecules drops to zero at a wavelength greater than 300 nm. Thermodynamic properties like energy, heat capacity, entropy, and enthalpy for all the studied molecules positively correlate with temperature, except the negative graph value of Gibbs free energy indicating the spontaneous behavior.
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Abstract Number: ANPA2024-N00081 Presenting Author: Kenan Gundogdu Presenter's Affiliation: NC State University Title: Room Temperature Perovskite Superfluorescence and its Implications for Quantum Materials Location: In-Person Presentation, Fayetteville Show/Hide Abstract The formation of coherent macroscopic states and the manipulation of their entanglement using external stimuli are essential for emerging quantum applications. However, the observation of collective quantum phenomena such as Bose–Einstein condensation, superconductivity, superfluidity and superradiance has been limited to extremely low temperatures to suppress dephasing due to random thermal agitations. In this presentation we will talk about room-temperature superfluorescence (SF) in hybrid perovskite thin films. In SF an optically excited population of incoherent dipoles develops collective coherence spontaneously. This emergent collective state forms a giant dipole and radiates a burst of photons. Because electronic transitions dephase extremely fast, observation of SF in semiconductors is extremely rare and under high magnetic fields and at very low temperatures. Therefore, the discovery of room temperature SF in perovskites is very surprising and shows that in this material platform, there exists an extremely strong immunity to electronic dephasing due to thermal processes. To explain this observation, we propose that the formation of large polarons in hybrid perovskites provides a quantum analogue of vibration isolation to electronic excitation and protects it against dephasing even at room temperature. Understanding the origins of sustained quantum coherence and the superfluorescence phase transition at high temperatures can provide guidance to design systems for emerging quantum information technologies and to realize similar high-temperature macroscopic quantum phenomena in tailored materials.
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Abstract Number: ANPA2024-N00082 Presenting Author: Ghadendra Bhandari Presenter's Affiliation: West Virginia University Title: Study of spontaneous magnetization reversal in manganites thin films Location: In-Person Presentation, Fayetteville Show/Hide Abstract Manganite perovskite compounds have gained interest among strongly correlated electron oxides. These systems have complex phase diagrams originating from interactions among charge, spin, and lattice degrees of freedom. Thin films of manganite compounds: LaMnO3 and La0.7Sr0.3MnO3 were developed on SrTiO3 substrates. The ferromagnetic behavior dominates in these films, and is the only clear type of magnetism when large magnetic fields are applied. However, when small applied magnetic fields are used, another magnetic behavior is also observed. These two magnetic behaviors interact in interesting ways, resulting in inverted hysteresis loops and negative magnetization in zero field cooled curves. This behavior could have interesting implications for spintronics, sensors and other applications. This work is partially supported by NASA EPSCoR Award# 80NSSC22M0173.
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Abstract Number: ANPA2024-N00083 Presenting Author: Basu Dev Oli Presenter's Affiliation: Department of Physics and Astronomy, West Virginia University, Morgantown, West Virginia 26506, USA Title: Determining alloy composition in superconducting single-layer FeSe1−xTex on SrTiO3(001) Substrates by Machine Learning of STM/S Data Location: In-Person Presentation, Fayetteville Show/Hide Abstract Chemical pressure from the isovalent substitution of Se by a larger Te atom in the epitaxial film of iron chalcogenide FeSe can effectively tune its superconducting, topological, and magnetic properties. In this study, we investigated the effects of chemical pressure in single-layer FeSe1−xTex films grown on SrTiO3(001) substrates by molecular beam epitaxy. The substitution of Se by Te during epitaxial growth inherently leads to defects and structural inhomogeneity, as observed in scanning tunneling microscopy (STM) images, making it challenging to determine the alloy composition. We utilize machine learning to distinguish between Se and Te atoms in STM images of these films. First, defect locations are identified by analyzing spatially dependent dI/dV tunneling spectra using the K-means clustering method. After excluding the defect regions, the remaining dI/dV tunneling spectra are analyzed using the singular value decomposition method to determine the Se/Te ratio [1]. Our findings present an effective and reliable approach for determining alloy composition and atomic-scale electronic inhomogeneity in superconducting single-layer iron chalcogenide films.
[1] Oli et al., “Atomic-scale electronic inhomogeneity in single-layer iron chalcogenide alloys revealed by machine learning of STM/S data”, AIP Adv. 13, 105224 (2023)
This research is supported by the U.S. Department of Energy, Office of Basic Energy Sciences, Division of Materials Sciences and Engineering (Grant Nos. DE-SC0017632 and DE-SC0021393).
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Abstract Number: ANPA2024-N00084 Presenting Author: Jett Wu Presenter's Affiliation: Fayetteville State University Title: Nano-Optimized Acetylcholinesterase Biosensor to monitor In Vitro and In Vivo Cholinergic Activity Location: In-Person Presentation, Fayetteville Show/Hide Abstract Acetylcholinesterase (AChE) inhibitors, such as chlorpyrifos, are widely used as pesticides and have been found to be harmful not only to pests but to humans as well. A common pest that affects crops is the bean beetle (Callosobruchus maculatus). We compared AChE activity obtained biochemically in bean beetles with AChE inhibition obtained electrochemically. The enzyme biosensor was constructed by immobilizing AChE onto MXene nanomaterials, which were attached to a conductive carbon cloth electrode surface. The presence of AChE inhibitors was then detected using this biosensor by electrochemical techniques, including differential pulse voltammetry (DPV), cyclic voltammetry (CV), and electrical impedance spectroscopy (EIS). A toxicity test that was run over a 72- hour period showed bean beetles exhibited a mortality rate of 62.5% following exposure to chlorpyrifos (CPF). AChE activity was inhibited In vivo by CPF. The In Vitro biochemical assay revealed AChE was inhibited by CPF. Other pesticides such as glyphosate, acephate, and permethrin did not inhibit AChE compared to controls for in vitro assays. The biosensor positively detected AChE inhibition for chlorpyrifos, acephate, and glyphosate, all known to inhibit AChE. Permethrin did not inhibit AChE biochemically or electrochemically. While the waveforms of DPV and CV did give data that support the findings, the clearest data to support the findings came from EIS, which suggests a correlation between the concentration of organophosphates and peak current. Our findings confirmed that biosensors may be more sensitive to AChE inhibitors than biochemical assays alone.
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Abstract Number: ANPA2024-N00096 Presenting Author: Bhoj Gautam Presenter's Affiliation: Fayetteville State University Title: Gamma Radiation Induced Structural Changes in Two Dimensional MXenes Location: In-Person Presentation, Fayetteville Show/Hide Abstract High electronic conductivity, structural diversity, and hydrophilicity of two dimensional MXenes opened broad prospects for their applications in variety of industrial and technological areas including energy storage, optoelectronics, spintronics, catalysis, and sensing. In this work, we studied the effect of gamma radiation on surface characteristics of mild etched Ti3C2TX MXene using Raman spectroscopy. Ti3C2TX MXene was synthesized by adding Ti3AlC2 powders into the LiF/HCl solution and was etched for 7 days at 70 °C. There are several spectral features apparent in the Raman Spectra. The peak ~200 cm−1 peak is related to A1g(Ti, O, C) band whereas peak ~ 720 corresponds to cm−1 A1g(C). These two Raman bands are highly diminished with the 1MGy dose of gamma radiation. The 150 cm−1 was enhanced in gamma irradiated sample indicating that gamma radiation activates the oxidation of surface titanium atoms. In addition, the different intensity of D (1350 cm−1) and G ( 1570 cm−1 ) bands between pristine and gamma irradiated MXenes indicates that the extent of amorphous carbon can also be tuned by gamma irradiation.
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Abstract Number: ANPA2024-N00097 Presenting Author: Dr. Nisha H. Makani Presenter's Affiliation: Fayetteville state university Title: Enhancing optical characteristics of Ti3C2 MXene quantum dots through hydrothermal and electrochemical synthesis methods Location: In-Person Presentation, Fayetteville Show/Hide Abstract The remarkable capabilities of Ti3C2 MXene quantum dots (QDs) have showcased their immense potential in various domains such as biological imaging, optical sensing, photoelectric conversion, etc. In this study, Ti3C2 QDs were synthesized via two distinct methodologies: hydrothermal and electrochemical routes. The hydrothermal approach involved the use of LiF and HCl to etch titanium aluminum carbide (Ti3AlC2), followed by controlled heating of the decanted solution to produce the QDs. Conversely, the electrochemical method employed a three-electrode configuration with Ti3AlC2 as the working electrode and an ionic liquid electrolyte to synthesize the QDs directly. Structural characterization was performed using X-ray diffraction (XRD) and Scanning electron microscopy (SEM), confirming the successful etching of aluminum from the Ti3AlC2 phase. Atomic force microscopy (AFM) and transmission electron microscopy (TEM) were used to measure the size of the QDs, which fell within the nanometer range, confirming the formation of QDs. Optical properties were assessed through UV-Vis spectroscopy and fluorescence lifetime measurements, showing distinct absorption and emission profiles for both sets of QDs. The hydrothermally synthesized QDs exhibited UV absorption between 200-220 nm and visible emission from 300-450 nm. Conversely, electrochemically synthesized QDs absorbed violet to blue light 350-400 nm with broader emission 400-500 nm, indicating the potential for various fluorescence imaging applications. This study showcases an expandable strategy for creating high-grade QDs with tunable optical features, catering to the needs of advanced optoelectronic devices.
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Abstract Number: ANPA2024-N00098 Presenting Author: Pravin Sharma Presenter's Affiliation: William & Mary Title: Atomistic Investigation of Ultrafast demagnetization of Permalloy films with varying laser fluence Location: In-Person Presentation, Fayetteville Show/Hide Abstract Permalloy (Ni80Fe20) is one of the soft ferromagnetic materials and promising for applications in spintronic devices with vanishing magnetic anisotropy and a remarkably high permeability with a diminishing coercive field. These properties are used for magnetometers, hard disk drive heads, and all-optical recording devices. For magneto-optic recording devices operating on a nanosecond timescale, the standard demagnetization technique is appropriate, but it is limited by the current speed at which magnetization can be manipulated. Employing ultrafast laser pulses holds immense potential in ferromagnetic permalloy in spin-based memory and storage devices with ultrafast processing speed which include laser-induced opto-magnetism. Here, we employ an atomistic spin dynamics model using a nearest-neighbor Heisenberg Hamiltonian exchange to study computationally the laser-induced magnetization dynamics. We study various timescales, various thicknesses of Permalloy thin films, and with varying laser fluences at different temperature. In addition to the ultrafast dynamics, we have also observed the precession frequency of the magnetization in the Permalloy layer at different temperatures with varying external magnetic fields. The atomistic simulations of the magnetization dynamics and precession frequency give good agreement with the experimental measurements for similar systems. Our work gives insight into the unification of ultrafast magnetic processes and its control over various timescales which can provide a guide to experiments directed to the future development of nanoscale devices in spintronics.
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Abstract Number: ANPA2024-N00099 Presenting Author: Tikaram Neupane Presenter's Affiliation: The University of North Carolina at Pembroke Title: Optical Properties of Cadmium Selenide Quantum Dots Location: In-Person Presentation, Fayetteville Show/Hide Abstract The optical properties of Cadmium Selenide (CdSe) Quantum Dots (QDs) play a pivotal role in modern technology, particularly in fields like optoelectronics, biomedical imaging, and solar cells, owing to their size-dependent tunable optical and electronic characteristics. This study focuses on characterizing optical properties of CdSe QDs including linear absorption, emission spectra, and exciton lifetime for varying sizes of 2.2 nm, 3.8 nm, and 6.5 nm in diameter. As anticipated, the absorption spectra exhibit a shift towards lower energy (or longer wavelength) as the QD size increases. The emission spectra of the QDs demonstrate a blue shift in frequency, with the emission energy lower than the first absorption peak, indicative of a Stokes shift. Specifically, the Stokes shifts were measured to be 17.1 nm, 18.4 nm, and 21.5 nm for QD sizes of 6.5 nm, 3.8 nm, and 2.2 nm, respectively. In addition, time-resolved spectroscopy is utilized to estimate optical bandgap-dependent exciton lifetime to understand the radiative and non-radiative decay process.
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Abstract Number: ANPA2024-N000105 Presenting Author: Krishna K C Presenter's Affiliation: University of Arkansas at Little Rock Title: Cost-effective and Sustainable Growth of Various Polymorphs of Tungsten Oxide Nanostructures for Energy Conversion and Storage Location: Virtual Presentation Show/Hide Abstract
Tungsten oxide exhibits a potential promise towards the sustainable and ecofriendly development of energy conversion, energy storage, catalysts and many other applications. The broad spectrum of its phase diagram is enriched with various distinct polymorphs of tungsten oxide ( 〖WO〗_x;2≤ x≤3 ). Due to their diverse structural, electronic, and optical properties, tungsten oxides have drawn attention among the scientific community. In addition to these properties, tungsten oxide nanostructures have shown their ability to enhance functional performance, due to an increase in surface-to-volume ratio. To utilize this material for sustainable functional device fabrication, there is a need to develop a cost effective, time efficient and green technique of synthesis. Here we have overcome these many challenges and successfully synthesized different polymorphs of tungsten oxide nanostructures by simply applying 2-6 W of power for a range of 2 – 60 min through utilizing simple scientific apparatus. Those oxides have shown effective performance towards energy conversion (Electrochemical Hydrogen Evolution) and energy storage (Super Capacitor) applications
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Abstract Number: ANPA2024-N000106 Presenting Author: Sadhana Vattikuti Presenter's Affiliation: Panther Creek High School, Cary, NC 27519, USA Title: Crystallography and DFT Investigation on Ta2C MXene Location: Virtual Presentation Show/Hide Abstract Since their first discovery in 2011, early transition metal carbide, nitride, or carbonitride with stoichiometric formula of Mn+1Xn, where M is an early transition metal such as Ti, Cr etc., X is C or N or CN and n is an integer greater than or equal to 1, called MXenes, have received great attention in the materials science community. MXenes have many excellent structural, electronic, magnetic, optical, and mechanical properties such as higher electrical and thermal conductivities, surface termination group dependent metallicity and magnetism, larger surface area for a given volume of a material, higher mechanical strength, and so on. In this project, we analyze crystallography of Ta2C MXene and its electronic structure, magnetism, and optical properties. Crystallographic analysis is done using the Visualization for Electronic STructural Analysis software known as VESTA. Electronic structure, magnetism and optics of Ta2C are studied using the first-principle Density Functional Theory (DFT) calculations using the Vienna Ab initio Simulation Package called VASP.
This work is supported by the Department of Energy BES-RENEW award number DE-SC0024611.
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Abstract Number: ANPA2024-N000107 Presenting Author: Raj Kumar Paudel Presenter's Affiliation: Postdoctoral Research Fellow, RCAS, Academia Sinica, Taiwan Title: Semiempirical Pseudopotential Method for Low-dimensional Materials Location: Virtual Presentation Show/Hide Abstract Semiempirical Pseudopotential Method for Low-dimensional Materials
Raj Kumar Paudel1, Chung-Yuan Ren2, and Yia-Chung Chang1,3
1Research Center for Applied Sciences, Academia Sinica, Taipei 115
2Department of Physics, National Kaohsiung Normal University, Kaohsiung 824, Taiwan
3Department of Physics, National Cheng-Kung University, Tainan 701, Taiwan
In recent years, there has been a significant focus on developing precise and efficient approaches to expedite Density Functional Theory (DFT) calculations for large unit cells. Among these techniques, the Semiempirical Pseudopotential Method (SEPM) [1] has emerged as a valuable tool for accurately determining band structures, especially in the realm of low-dimensional materials. SEPM operates by utilizing atomic pseudopotentials, which are derived from DFT calculations. Significantly, SEPM calculations offer a unique advantage compared to DFT as they eliminate the requirement for iterative self-consistent solutions in solving the Schrödinger equation, leading to a substantial reduction in computational complexity.
The incorporation of both non-local and local Semiempirical Pseudopotentials in our current approach yields band structures and wavefunctions with enhanced precision compared to traditional empirical methods [2]. When applied to graphene, our model's computed band structure closely aligns with that obtained via DFT calculations [3]. Impressively, our method demands only a fraction of the time required in comparison to the CG iterative solver with self-consistent charge density from DFT. Additionally, we utilized the SEPM technique for armchair graphene nanoribbons (aGNR), achieving results that closely align with those obtained through DFT, but with significantly reduced computational time. Furthermore, we extended the application of our SEPM approach to monolayer TMDCs, adjusting the parameters to align with pertinent values obtained from DFT computations. This enables us to faithfully replicate the band structure, opening avenues for investigating the optoelectronic properties of TMDCs and exploring their potential applications in nanodevices.
References
[1] Paudel, R.K.; Ren, C.-Y.; Chang, Y.-C. Semi-Empirical Pseudopotential Method for Graphene and Graphene Nanoribbons. Nanomaterials 2023, 13,2066
[2] Chelikowsky, J.R.; Cohen, M.L. Nonlocal pseudopotential calculations for the electronic structure of eleven diamond and zinc-blende semiconductors. Phys Rev B. 1976, 14, 556.
[3] Ren C.Y.; Hsue, C.S.; Chang Y.C. A Mixed Basis Density Functional Approach for Low-Dimensional Systems with B-splines. Computer Physics Communication. 2015, 188, 94-102
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Abstract Number: ANPA2024-N000108 Presenting Author: Anup Pradhan Sakhya Presenter's Affiliation: University of Central Florida Title: MANIFESTATION OF CORRELATED ELECTRONIC STRUCTURE IN A KAGOME METAL YbTi3Bi4 Location: Virtual Presentation Show/Hide Abstract Kagome lattices have emerged as an ideal platform for exploring various exotic quantum phenomena such as correlated topological phases, frustrated lattice geometry, unconventional charge density wave orders, Chern quantum phases, superconductivity, etc. Here, we report the discovery of a new Ti-based kagome metal YbTi3Bi4 which is characterized using angle-resolved photoemission spectroscopy (ARPES) and magneto-transport, in combination with density functional theory calculations. Our ARPES results reveal the complex fermiology of this system along with the spectroscopic evidence of four flat bands. Furthermore, our electronic structure measurements show the presence of multiple van Hove singularities originating from Ti 3d orbitals. We have identified that the system exhibits topological nontriviality with surface Dirac cones at the Γ point and a bulk linearly dispersing gapped Dirac-like state at the K point as indicated by our theoretical calculations. These results establish YbTi3Bi4 as a novel platform for exploring the intersection of nontrivial topology, and electron correlation effects in the wider LnTi3Bi4 (Ln= lanthanide) family of materials.
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Abstract Number: ANPA2024-N000109 Presenting Author: Arun Kumar Kumay Presenter's Affiliation: University of Central Florida Title: Electronic structure in a transition metal dipnictide TaAs2 Location: Virtual Presentation Show/Hide Abstract The family of transition-metal dipnictides (TMDs) has been of theoretical and experimental interest because this family hosts topological states and extremely large magnetoresistance (MR). Recently, TaAs2, a member of this family, has been predicted to
support a topological crystalline insulating state. Here, by using high-resolution angle-resolved photoemission spectroscopy (ARPES), we reveal both closed and open pockets in the metallic Fermi surface and linearly dispersive bands on the (2 ̅01) surface, along with the presence of extreme MR observed from magneto-transport measurements. A comparison of the ARPES results with first-principles computations shows that the linearly dispersive bands on the measured surface of TaAs2 are trivial bulk bands. The absence of
symmetry-protected surface state on the (2 ̅01) surface indicates its topologically dark nature. The presence of open Fermi surface features suggests that the open orbit fermiology could contribute to the extremely large MR of TaAs2.
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Abstract Number: ANPA2024-N000110 Presenting Author: Mazharul Islam Mondal Presenter's Affiliation: University of Central Florida Title: Observation of multiple flat bands and Van-Hove Singularities in a distorted kagome system NdTi3Bi4. Location: Virtual Presentation Show/Hide Abstract Kagome materials have attracted enormous research interest recently owing to their diverse topological phases and manifestation of electronic correlation due to their inherent geometric frustration. Here, we report the electronic structure of a distorted Kagome metal NdTi3Bi4 using a combination of angle-resolved photoemission spectroscopy (ARPES) measurements and density functional theory (DFT) calculations. We discover the presence of two “flat” bands which are found to originate from the Kagome structure formed by Ti atoms with major contribution from Ti dxy and Ti dx2−y2 orbitals. We also observed multiple van Hove singularities (VHSs) in its electronic structure, with one VHS lying near the Fermi level (EF). Our calculation indicates the presence of linear band at the Γ point and a linear Dirac-like state at the K point with its Dirac node located very close to the EF. Our findings reveal NdTi3Bi4 as a potential material to understand the interplay of topology, and magnetism.
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Abstract Number: ANPA2024-N000115 Presenting Author: Sekh Jamaluddin Presenter's Affiliation: Department of Physics and Astronomy, University of Notre Dame, Notre Dame, In 46556, USA Title: Real-space observation of non-trivial spin textures in Ga-doped TmMn6Sn6 kagome magnet Location: Virtual Presentation Show/Hide Abstract Magnetic Skyrmions are topologically protected vortex types of incommensurate spin textures with a fixed topological number. The particle-like behavior and ability to move with low deepening current density make them potential candidates in future spintronics devices. Designing new material systems by tuning the governing interactions to stabilize and manipulate Skyrmionic spin textures holds significant importance from both practical and fundamental perspectives. In non-centrosymmetric systems, the key mechanism for stabilizing Skyrmion spin states is the competition between the exchange interaction and Dzyaloshinskii-Moriya interaction (DMI). On the contrary, in centrosymmetric systems, the stabilization of these non-trivial spin textures is driven by the competition between dipolar interaction and out-of-plane magnetic anisotropy. Here, utilizing Lorentz Transmission Electron Microscopy (LTEM), we present the real space observation of magnetic Skyrmion bubbles in Ga doped TmMn6Sn6 kagome magnet. At zero field, we have observed stripe domains as the ground state, and they break into Skyrmion bubbles in the presence of an external magnetic field. Our magnetization measurements reveal that the partial replacement of the non-magnetic atom Sn with Ga drives the systems from easy plane anisotropy to an easy axis anisotropy system, a crucial condition for stabilizing Skyrmionic states. Our findings present a wide range of opportunities to design new materials, particularly the 166 kagome magnets, by tuning the intrinsic properties of the materials to create and manipulate the various non-trivial spin textures.
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Abstract Number: ANPA2024-N000116 Presenting Author: Abhijeet Nayak Presenter's Affiliation: Department of Physics and Astronomy, University of Notre Dame; Stavropoulos Centre for Complex Quantum Matter, University of Notre Dame Title: Crystal Growth and Magnetic properties of RFe6Ge6 (R= Tb, Dy) Location: Virtual Presentation Show/Hide Abstract Rare earth based magnetic compounds are the promising family of materials with non-trival phenomena arising from the correlation between the electronic structure and magnetism. The interplay between the conduction electrons with the band topology gives exciting physical properties. In this study, we have successfully synthesized single crystals of RFe₆Ge₆ (R = Tb, Dy) using flux growth methods. The structural characterization are studied using powder X-ray diffraction (XRD), which reveals an orthorhombic structure with the space group Cmcm. Here we discuss the results of magnetization and magneto-transport measurements done on single crystals of TbFe6Ge6 and DyFe6Ge6. Our methods of growing single crystal of RFe6Ge6 and findings of their physical properties will be useful to explore other possible findings in this large family of materials which was limited to the study of mostly polycrystalline samples in past. The detailed analysis of the crystal growth techniques, magneto-transport measurements, and theoretical studies might be a robust foundation for future research and development in this area.
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Abstract Number: ANPA2024-N000117 Presenting Author: Hari Bhandari Presenter's Affiliation: Department of Physics and Astronomy, University of Notre Dame; Stavropoulos Centre for Complex Quantum Matter, University of Notre Dame Title: Role of Ga doping in the kagome ferromagnet YMn6Sn6-xGax Location: Virtual Presentation Show/Hide Abstract Kagome magnets are an interesting class of materials and an ideal platform to study the interplay between topology, magnetism, and electronic correlation. YMn6Sn6 is one such compound which orders with a commensurate antiferromagnetic helical structure below 345 K and exhibits an incommensurate double helical structure (DH) upon further cooling. Previous studies have shown that YMn6Sn6-xGax evolves from incommensurate antiferromagnet to ferromagnet for x>0.2, but its microscopic origin has remained unclear. Here, we will talk about the role of Ga doping on the electronic and magnetic properties for YMn6Sn6-xGax (x~1).
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Abstract Number: ANPA2024-N000118 Presenting Author: Suresh Gnawali Presenter's Affiliation: Georgia State University Title: High-order harmonic generation in graphene quantum dots in the field of an elliptically polarized optical pulse Location: Virtual Presentation Show/Hide Abstract
We study theoretically the generation of high-order harmonics in graphene quantum dots placed in the field of an elliptically polarized ultrashort pulse. The generated high-order harmonics are sensitive to the pulse's ellipticity and amplitude. The intensities of high-order harmonics become very sensitive to the ellipticity of an incident pulse when its polarization gets close to a circular one, and some high-order harmonics become strongly suppressed for a circularly polarized incident pulse. The suppressed harmonic orders depend on the symmetry of the quantum dot systems. Every third harmonic is suppressed for triangular quantum dots, which have D3h symmetry. In contrast, for hexagonal quantum dots with D6h symmetry, such suppression is observed for every sixth harmonic, and the even-order harmonics are suppressed for all ellipticities of the incident pulse due to an additional inversion symmetry of the hexagonal quantum dots. The ellipticities of the generated high-order harmonics also show strong nonmonotonic dependence on the ellipticity of an incident pulse, in which the dependence becomes stronger for high pulse amplitudes.
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Abstract Number: ANPA2024-N000119 Presenting Author: Tika R Kafle Presenter's Affiliation: JILA, University of Colorado Boulder Title: Non-equilibrium States and Interactions in the Topological Insulator and Topological Crystalline Insulator Phases of NaCd4As3 Location: Virtual Presentation Show/Hide Abstract The non-equilibrium dynamics of a dual topological phase material, NaCd4As3, is investigated using high harmonic generation (HHG) based time and angle resolved photoemission spectroscopy (tr-ARPES). In its topological insulator (TI) phase, at temperatures below ~195 K, a gradual evolution of the chemical potential shift >150 meV is observed when excited by an ultrafast laser pulse. We attribute this change to the increased phase space density near Fermi level that is induced during the relaxation process of the partially distorted TI lattice phase. Such strong coupling of electronic and structural orders is supported by the slow rise (~0.6 ps) and fall time (~8 ps) of the excited electron population and electron temperature. In contrast in the TCI phase at temperatures above ~195 K, no distinct excited state is observed after photoexcitation––which we attribute to the low density of states and phase space available near the Fermi level. Our results show how excitation by ultrafast light pulses can probe the excited states and interactions within phase rich topological materials.
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