The field of ‘Condensed Matter and Materials Science’ combines physics and chemistry to understand the behavior of materials around us. This covers a broad range of topics including but not limited to:
Structural, Electronic, Magnetic, and Optical Properties of Materials; Quantum Phenomena and Materials (Topological, Semimetals, and Quantum Information); Quantum Coherence; Van der Waals Interactions in 2D Materials, Excited-State Phenomena; Energetic Materials, High Entropy Materials; Permanent Magnets; Superconductivity; Quantum Hall Effect; Magnetocaloric Materials and Phenomena; Materials Design and Discovery; Novel Oxides; Rare Earth Materials; Semiconductors: Electronic, Photonics and Optoelectronics; Magneto-Transports and Magnetic Interfaces
Electronic structure evolution in magnetic topological materials
The discovery of topological insulators (TIs) has prompted intensive theoretical and experimental studies
on realizing various topological states in quantum materials. Owing to the bulk-boundary correspondence,
the TIs support conducting surface states that lie within the gapped bulk electronic spectrum of the TIs. These
surface states are spin polarized and disperse linearly with Dirac-cone energy dispersion. Constraints of the
time-reversal symmetry protect the surface states from backscattering and localization in the presence of
nonmagnetic perturbations thereby making TIs promising for low-power energy-efficient quantum electronic
applications. Recently, new types of topological materials inspired by magnetism have attracted intensive
research interest. In this talk, I will discuss electronic structure evolution across the magnetic transition
temperature for rare-earth monopnictide based materials and kagome magnets. Our study indicates that
magnetism plays an intricate role in the electronic structure of the topological material family.
Biologically Active Natural Products: Characterization and Quantum Mechanical Calculations
Natural products are the compounds extracted from living things: plants, animals, and marine organisms [1]. Due to their structural and electronic activities, they play a vital role in the treatments of several diseases in humans as well as in animals even in life-threatening conditions. Vibrational spectroscopy in addition to quantum chemical methods are been used since a decade back for molecular characterization [2,3]. Vibrational frequency analysis, inter/intra-molecular charge transfer, charge delocalization, molecular electrostatic potential, binding sites, protein-ligand interaction, protein-protein interaction are some properties for understanding the structure-electronic behavior of the molecular system. We have investigated structural, electronic, vibrational, and nonlinear optical properties of aristolochic acid, oncocalyxone A, canadine, ricobendazole, cephalexin, etc molecules by density functional theory (DFT) using Gaussian 09 program at 6-311++g(d,p) level. Canadine, an active component of Goldenseal, gives 132 modes of vibration. The electronic absorption in EtOH solvent phase was recorded at 294 and 386nm. Oncocalyxone A, an antiplatelet and known for the treatment of cuts and wounds, gives 114 modes of vibration. The electronic absorption in the methanol environment was recorded at 495 and 280nm. Chemical calculations on ricobendzole and cephalexin supported their good inhibitor property for the predicted target proteins [4].
References:
[1] D.J Faulkner, Marine natural products, Nat. Prod. Repts., 2000 17(1) 1.
[2] B.D. Joshi, R. Mishra, P. Tandon, A.C. Oliveira, A.P. Ayala, J. Mol. Struct. 1058 (2014) 31
[3] J. de Castro Fonseca, Y.S. de Oliveira, et al., Spectrochim. Acta Part A: Mol. Biomol. Spectrosc. 165 (2016) 26.
[4] M.K. Chaudhary, P. Prajapati , K. Srivastava, K. F. Silva, B.D. Joshi, P. Tandon, A.P. Ayala, J. Mol. Struct. 1230 (2021) 129889.
Session Schedule
Please look below for detailed schedule.
|
Date/Time: |
Abstract Number: ANPA2022_0124 Presenting Author: Ram Babu Ray Presenter's Affiliation: Central Department of Physics, Kirtipur, Kathmandu, Nepal Title: Electronic Structures, Magnetic Properties and Strain Effects of Quaternary Heusler Alloy ZrRuTiIn Show/Hide Abstract Electronic Structures, Magnetic Properties and Strain Effects of Quaternary Heusler Alloy
ZrRuTiIn
R. B. Ray 1 and G. C. Kaphle 2
1
Central Department of Physics, Tribhuvan University, Kirtipur,
Kathmandu, Nepal
2
Central Department of Physics, Tribhuvan University, Kirtipur,
Kathmandu, Nepal
*Email: ray-rb@ymail.com
Abstract
Electronic and magnetic properties of quaternary Heusler alloy ZrRuTiIn have been analyzed by using
density functional theory (DFT) based Wien2k approach. The optimized structure of ZrRuTiIn is
obtained through the energy minimization process. The ferromagnetic ground state and
thermodynamical stability of compound is supported by relative total energy and by derived cohesive
energy respectively. From the study, the quaternary Heusler alloy ZrRuTiIn shows half-metallic
ferromagnetic and spin-polarized density of states (DOS). The spin dependent band gap, that is, Half-
metallic gap of ZrRuTiIn is 0.61 eV. We have obtained unsymmetrical nature of DOS in up and down
spin channels. The total spin magnetic moment of ZrRuTiIn is 1.00 ? B , which is integral value
supporting HMF nature of ZrRuTiIn. Detailed study of strain effects of quaternary Heusler alloy
ZrRuTiIn will be comprehensibly presented.
Key words: Quaternary Heusler alloy, Density of states
References
1. F. Dahmane et al., Journal of Superconductivity and Novel Magnetism 28, 2063-2069 (2015).
2. L. Feng et al., Journal of Magnetism and Magnetic Material 351, 92-97 (2014).
3. S. M. Azar et al., Journal of Magnetism and Magnetic Material 10, 324 (2007).
4. Saadi Berri et al., Computational Condensed Matter 1, 26-31 (2014).
|
||||||
|
Date/Time: |
Abstract Number: ANPA2022_0110 Presenting Author: Iftakhar Bin Elius Presenter's Affiliation: University of Central Florida (UCF) Title: Effect of dilute magnetism in a topological insulator Show/Hide Abstract Three-dimensional topological insulator (TI) has emerged as a unique state of quantum matter and generated enormous interests in condensed matter physics. The surfaces of a three-dimensional TI consist of a massless Dirac cone, which is characterized by the Z2 topological invariant. Introduction of magnetism on the surface of a TI is essential to realize the quantum anomalous Hall effect and other novel magneto-electric phenomena. Here, by using a combination of first-principles calculations, magneto-transport and angle-resolved photoemission spectroscopy (ARPES), we study the electronic properties of gadolinium (Gd)-doped Sb2Te3. Our study shows that Gd doped Sb2Te3 is a spin-orbit-induced bulk band-gap material, whose surface is characterized by a single topological surface state. Our results provide a new platform to investigate the interactions between dilute magnetism and topology in magnetic doped topological materials.
|
||||||
|
Date/Time: |
Abstract Number: ANPA2022_0111 Presenting Author: Dipendra Dahal Presenter's Affiliation: University of Houston Title: plasmonic behavior of silicene and graphene based heterostructure Show/Hide Abstract The Coulomb excitations of charge density oscillation are calculated for a double layer heterostructure. Specifically, we consider two-dimensional (2D) layers of silicene and graphene on a substrate.
From the obtained surface response function, we calculated the plasmon dispersion relations which
demonstrate the way in which the Coulomb coupling renormalizes the plasmon frequencies. Additionally, we present a novel result for the damping rates of the plasmons in this Coulomb coupled
heterostructure and compare these results as the separation between layers is varied.
|
||||||
|
Date/Time: |
Abstract Number: ANPA2022_0112 Presenting Author: Niraj Aryal Presenter's Affiliation: Brookhaven National Laboratory Title: Origin of the metal-insulator transition in the parent compounds of Ru-pnictide superconductors Show/Hide Abstract We study the interplay of the structural phase transition and metal-insulator transition in the
parent compunds of the Ru-pnictide superconductor family. We find that while RuP and RuAs undergo metal-insulator transition accompanied by orthorhombic to monoclinic distortion, RuSb stays orthorhombic and metallic. By using first principles and effective Hamiltonian calculations, we study the electronic and phononic dispersion of these systems and explain the origin of the instability and its implications to the superconductivity.
|
||||||
|
Date/Time: |
Abstract Number: ANPA2022_0113 Presenting Author: Yangyang Liu Presenter's Affiliation: University of Central Florida Title: Ultrafast relaxation of acoustic and optical phonons in a topological nodal-line semimetal ZrSiS Show/Hide Abstract Recently, nodalline semimetals based on ZrSiS-family have garnered massive research interests contributing numerous experimental and theoretical works. Despite being the most studied nodal-line semimetal, a clear understanding of the transient state relaxation dynamics and the underlying mechanism in ZrSiS is lacking. Using time- and angle-resolved photoemission spectroscopy, we study the ultrafast relaxation dynamics in ZrSiS and reveal a unique relaxation in the bulk nodalline state which is well-captured by a simple model based on optical and acoustic phonon cooling. Our model predicts linear decay processes for both optical and acoustic phonon relaxations with optical cooling dominant at higher temperatures. Our results reveal different decay mechanisms for the bulk and surface states and pave a way to understand the mechanism of conduction in this material.
|
||||||
|
Date/Time: |
Abstract Number: ANPA2022_0114 Presenting Author: Amba Datt Pant Presenter's Affiliation: Institute of Materials Structure Science, High Energy Accelerator Research Organization (KEK),1-1 Oho, Tsukuba, Ibaraki 305-0801, and Muon Section, Materials and Life Science Division, J-PARC center, 2-4 Shirane Shirakata, Tokai-mura, Naka-gun, Ibaraki 319-1195, Japan Title: New insight into muSR in water Show/Hide Abstract Over the past four decades, muon spin rotation and relaxation (muSR) technique in water and ice has been reported by several groups. Most of the previous studies were focused on muonium (Mu = u+e-) chemistry (detection, its relaxation, reaction and frequencies) in water and ice. The behavior of muon in ice and water is not clearly understood yet.
Since the water is indispensable component in materials and life sciences, the detailed study of muon and Mu in ice and water is necessary to understand/apply the muon technique to wide variety of sciences like life sciences, medical/clinical fields, etc. In order to apply the muon method for detection of oxygen in hypoxia in tumor, electron transfer in protein, function of DNA, photosynthesis, etc., we have started the systematic experimental and theoretical study in water and constituents of protein towards whole targeted system. In the program, brief review and recent achievements (experimental results and theoretical interpretation using DFT calculations and Quantum simulation) in muSR studies in water and ice will be presented.
|
||||||
|
Date/Time: |
Abstract Number: ANPA2022_0118 Presenting Author: Bhawani Datt Joshi (Invited) Presenter's Affiliation: Department of Physics, Siddhanath Science Campus, Mahendranagar, TU, Nepal Title: Biologically Active Natural Products: Characterization and Quantum Mechanical Calculations Show/Hide Abstract Natural products are the compounds extracted from living things: plants, animals, and marine organisms [1]. Due to their structural and electronic activities, they play a vital role in the treatments of several diseases in humans as well as in animals even in life-threatening conditions. Vibrational spectroscopy in addition to quantum chemical methods are been used since a decade back for molecular characterization [2,3]. Vibrational frequency analysis, inter/intra-molecular charge transfer, charge delocalization, molecular electrostatic potential, binding sites, protein-ligand interaction, protein-protein interaction are some properties for understanding the structure-electronic behavior of the molecular system. We have investigated structural, electronic, vibrational, and nonlinear optical properties of aristolochic acid, oncocalyxone A, canadine, ricobendazole, cephalexin, etc molecules by density functional theory (DFT) using Gaussian 09 program at 6-311++g(d,p) level. Canadine, an active component of Goldenseal, gives 132 modes of vibration. The electronic absorption in EtOH solvent phase was recorded at 294 and 386nm. Oncocalyxone A, an antiplatelet and known for the treatment of cuts and wounds, gives 114 modes of vibration. The electronic absorption in the methanol environment was recorded at 495 and 280nm. Chemical calculations on ricobendzole and cephalexin supported their good inhibitor property for the predicted target proteins [4].
Reference
[1] D.J Faulkner, Marine natural products, Nat. Prod. Repts., 2000 17(1) 1.
[2] B.D. Joshi, R. Mishra, P. Tandon, A.C. Oliveira, A.P. Ayala, J. Mol. Struct. 1058 (2014) 31
[3] J. de Castro Fonseca, Y.S. de Oliveira, et al., Spectrochim. Acta Part A: Mol. Biomol. Spectrosc. 165 (2016) 26.
[4] M.K. Chaudhary, P. Prajapati , K. Srivastava, K. F. Silva, B.D. Joshi, P. Tandon, A.P. Ayala, J. Mol. Struct. 1230 (2021) 129889.
|
||||||
|
Date/Time: |
Abstract Number: ANPA2022_0119 Presenting Author: Sujan Shrestha Presenter's Affiliation: Department of Physics and Astronomy, University of Kentucky Title: Emergent La2CuO4-like interlayer antiferromagnetic magnetic order induced via orthorhombic-distortion in Sr2IrO4 Show/Hide Abstract We report a distinct La2CuO4-like interlayer antiferromagnetic stacking order in Sr2IrO4 thin films by introducing large orthorhombic distortion (> 1.5%) via anisotropic biaxial lattice strain in Sr2IrO4/Ca3Ru2O7 heterostructures. The orthorhombic distortion stabilizes the Jeff = � pseudospin moment direction along the longer lattice direction via magnetic anisotropy while it lead to non-zero interlayer exchange interaction energy. Resonant X-ray magnetic scattering confirms that the magnetic moment is parallel to the elongated b-axis whereas its stacking pattern is inverted from that of the tetragonal Sr2IrO4 crystal. This combination corresponds to the La2CuO4-type interlayer antiferromagnetic order which can be explained by the competition between interlayer interaction energies such that the net asymmetric interlayer exchange interaction energy between a and b-axes exceed the interlayer pseudo-dipolar interaction energy. Our result suggests that anisotropic strain-induced orthorhombic distortion provides a delicate knob for tuning the long-range magnetic order and enhancing the magnetic quantum fluctuations in quasi-two-dimensional systems.
|
||||||
|
Date/Time: |
Abstract Number: ANPA2022_0120 Presenting Author: Jhulan Powrel Presenter's Affiliation: Tribhuvan University Title: Binding Free Energy of Sickle and Normal Hemoglobin Dimer Protein: Umbrella Sampling Molecular Dynamics". Show/Hide Abstract This study focuses on investigation of the binding mechanism of different chains of hemoglobin under the mutated condition which can give the understanding on the molecular distortion. In this work, we have studied the binding mechanism between two chains of R-state conformation of carbonmonoxyl sickle hemoglobin and is compared with that of normal hemoglobin by using molecular dynamics simulations. The binding strength has been analyzed by estimating hydrogen bonding, salt bridges, hydrophobic interactions and non-bonded interactions (electrostatics and van der Waals). The comparative outcomes in two structures show that the binding strength of ?? and ?? chains in normal hemoglobin is higher than that of sickle hemoglobin due to vdW and electrostatic interaction in between chain ?? and chains ?? in the dimer showing the favorable binding in normal hemoglobin
than sickle. Structural stability is controlled by hydrophobic interactions of both protein. The sickling is occurring due to higher hydrophobic interaction of sickle than of normal hemoglobin. Binding strength of the molecule have also been investigated by estimating binding free energy, utilizing umbrella sampling technique. The binding free energy difference in sickle and normal hemoglobin dimer is found to be ? 0.67 kcal/mol. The results given by the aforementioned interactions are also supported by binding free energy calculation.
|
||||||
|
Date/Time: |
Abstract Number: ANPA2022_0121 Presenting Author: Yogesh Singh Maharjan Presenter's Affiliation: Amrit Campus, Tribhuvan University Title: EFFECT OF THICKNESS ON ZnO THIN FILM PREPARED BY DIP COATING TECHNIQUE FOR ETHONAL SENSING Show/Hide Abstract 0.5M Zinc Oxide (ZnO) nano-particle thin films were deposited on cleaned glass substrates by dip coating technique with 350 mm/min dipping speed. These films were optically characterized using UV-Vis spectrophotometer. The band gap of film was found to be 3.11 eV having thickness 903.176 nm. Thickness was measured using a Swanepoel method. The refractive index of ZnO was also measured and its value was found to be 2.091 -1.532 in the wavelength of 350-800 nm. The prepared ZnO thin film was used to detect ethanol vapor in the temperature range 180 to 300 �C. The highest response of 3.4 was found at the operating temperature of 240 �C for 500 ppm of ethanol vapor. Corresponding response and recovery times were found as 9.82 and 16.33 sec respectively.
|
||||||
|
Date/Time: |
Abstract Number: ANPA2022_0122 Presenting Author: Sabin Regmi Presenter's Affiliation: Department of Physics, University of Central Florida, Florida 32816, USA Title: Observation of multiple nodal-lines in SmSbTe Show/Hide Abstract The ZrSiS-type LnSbTe (Ln = lanthanide elements) materials have been attracting research studies due to possible magnetism and correlation effects carried by 4f electrons of the lanthanide elements, therefore providing important platform to study the interplay among topology, magnetism, and correlation. Here, we report the electronic structure of SmSbTe measured by using angle-resolved photoemission spectroscopy along with parallel first-principles calculations, transport, and magnetic measurements. Our results identify multiple Dirac nodes along the ? � X and Z � R directions that correspond to the nodal-lines predicted by our theoretical calculations. A surface Dirac-like state is also observed at the X point of the surface Brillouin zone. Our study highlights SmSbTe as a promising candidate to understand the topological electronic structure of LnSbTe materials.
This project is supported by the National Science Foundation (NSF) CAREER award DMR-1847962, the Air Force Office of Scientific Research under award number FA9550-17-1-0415, the Air Force Office of Scientific Research MURI Grant No. FA9550-20-1-0322, and the Center for Thermal Energy Transport under Irradiation, an Energy Frontier Research Center funded by the U.S. DOE, Office of Basic Energy Sciences.
|
||||||
|
Date/Time: |
Abstract Number: ANPA2022_0123 Presenting Author: Tibendra Adhikari Presenter's Affiliation: Central Department of Physics, Kirtipur, Kathmandu, Nepal Title: First-principles study of defected silicene for the adsorption of methane gas molecule Show/Hide Abstract
First-principles study of defected silicene for the adsorption of methane gas molecule
Tibendra Adhikari and Nurapati Pantha
Central Department of Physics, Tribhuvan University, Kirtipur, Kathmandu, Nepal
Considering the significance of natural gas, such as methane, and the difficulties in storing it, research is increasingly focusing on developing materials for solid-state methane storage. Two-dimensional materials have a large number of possible adsorption sites for gas molecules due to their high surface-to-volume ratio. However, the two-dimensional structure is chemically inactive and attracts nonpolar gases rather weakly [1]. We investigated the methane gas adsorption capabilities of silicene by activating it with different defects [2,3]. According to our density functional theory calculations, the mono-vacancy (MV) defect is advantageous in increasing the binding strength of energy-carrying gases such as methane. In MV defected silicene, methane adsorption energy is detected in the order of the internationally specified energy regime [4].
Acknowledgement
The authors acknowledge the TWAS research grants RG 20- 316 for providing computational help.
References
1. R. B. Bird, W. E. Stewart, and E. N. Lightfoot, Transport phenomena, Vol. 1 (John Wiley & Sons, 2006).
2. S. M. Aghaei, M. M. Monshi, and I. Calizo, RSC Adv. 6, 94417 (2016).
3. N. Pantha, K. Ulman, and S. Narasimhan, J. Chem. Phys. 153, 244701 (2020).
4. S. K. Bhatia and A. L. Myers, Langmuir 22, 1688 (2006).
|
||||||
|
Date/Time: |
Abstract Number: ANPA2022_0150 Presenting Author: Sunil K. Karna Presenter's Affiliation: Norfolk State University Title: Mesoscopic magnetic modulation in chiral helimagnet Mn1/3NbS2 Show/Hide Abstract We have investigated the magnetic state of Mn1/3NbS2 through x-ray and neutron diffraction, magnetization, ac-magnetic susceptibility, small-angle Neutron Scattering (SANS), Lorentz Transmission Electron Microscopy (LTEM) and micromagnetic simulations. The ac susceptibility displays temperature, field, and frequency dependencies which define a complex phase diagram below the critical temperature for magnetic ordering, TC = 45 K. SANS reveals a streak of magnetic scattering along the c-axis near Q = 0 appearing below TC, demonstrating a disordered ferromagnetic (FM) or helical spin ordering in this system. The width of this streak shortens and becomes more intense near TC and is gradually suppressed by the application of H along the beam. Micromagnetic simulations of thin lamella agree with LTEM images of Mn1/3NbS2 where extended FM regions result from a shape anisotropy in thin samples that are separated by chiral domain walls.
|
||||||
|
Date/Time: |
Abstract Number: ANPA2022_0152 Presenting Author: Bibek Singh Dhami Presenter's Affiliation: University of Alabama at Birmingham Title: Angle-Resolved Cathodoluminescence Imaging Polarimetry of Hybrid Perovskites Show/Hide Abstract Hybrid perovskites have attracted immense interest in short period of time for advanced opto-electronic and energy harvesting applications. Understanding how photons couple with these materials is of great importance. Perovskite community has done intense research on studying the spectral content and quantum efficiency of emitted photons, little has been explored about other properties such as emission directionality and polarization. Herein, we used angle-resolved cathodoluminescence microscopy to access the polarization state of emitted photons with spatial resolution well below the optical diffraction limit. We explore the effect of grain boundary on the degree of polarization and angle of emitted photons that provide significant understanding of emission properties of hybrid perovskites.
|
||||||
|
Date/Time: |
Abstract Number: ANPA2022_0153 Presenting Author: Nabin Kumar Raut Presenter's Affiliation: University of California, Merced Title: Magnetic levitation within a microwave cavity: characterization, challenges, possibilities, and experiments Show/Hide Abstract The low energy losses in the superconducting magnetic levitation makes it attractive for the exciting applications in physics. The Meissner levitation has been proposed for the study of modified gravitational wave detection [1]. Furthermore, the levitated magnet is coupled to the individual spin qubit in the nitrogen-vacancy center to read out the qubit state [2]. Meissner levitation within the microwave cavity could open avenues for the novel cavity optomechanical system, readout for quantum object such as the transmon, and magnon, gravitational wave detection, and magnetomechanics. This presentation characterized Meissner levitation of a permanent neodymium magnet within a microwave cavity [3,4]. It also discusses possibilities, challenges, and cryogenic experiments.
References
[1] C. Timberlake, A. Vinante, F. Shankar, A. Lapi, and H. Ulbricht, Physical Review D 104 (2021).
[2] J. Gieseler, A. Kabcenell, E. Rosenfeld, J. D. Schaefer, A. Safira, M. J. Schuetz, C. Gonzalez-Ballestero, C. C. Rusconi, O. Romero-Isart, and M. D. Lukin, Phys. Rev. Lett. 124, 163604 (2020).
[3] N. Raut, J. Miller, J. Pate, R. Chiao, and J. Sharping, IEEE Trans. Appl. Supercond. (2021).
[4] N. K. Raut, J. Miller, R. Chiao, and J. E. Sharping, arXiv preprint arXiv:2101.01309 (2021).
|
||||||
|
Date/Time: |
Abstract Number: ANPA2022_0156 Presenting Author: Bashu Dev Khanal Presenter's Affiliation: Old Dominion University Title: Effect of successive heat treatment on the performance of superconducting radio-frequency niobium cavities Show/Hide Abstract One of the primary sources of rf residual losses leading to lower quality factor (Q0 )
is trapped residual magnetic field during the cooldown of superconducting radio
frequency (SRF) cavities. It has been reported that non-uniform recrystallization of
niobium cavities after the post fabrication heat treatment leads to higher flux
trapping during the cooldown, and hence the lower Q0 . Here, we fabricated several
1.3 GHz single cell cavities from high purity fine grain Nb with different
microstructure and processed with successive heat treatments in the range 800 �
1000 ?C to measure the flux expulsion and flux trapping sensitivity. The results
show the improved flux expulsion with increase in heat treatment temperature and
flux trapping sensitivity depends on the final surface preparation prior to the rf test.
This manuscript has been authored by Jefferson Science Associates, LLC under U.S. DOE
Contract No. DE-AC05-06OR23177. The work done at Florida State University is supported by
the U.S. Department of Energy, Office of Science, Office of High Energy Physics under Awards
No. DE-SC 0009960
|
||||||
|
Date/Time: |
Abstract Number: ANPA2022_0165 Presenting Author: Madhab Neupane (Invited) Presenter's Affiliation: University of Central Florida Title: Electronic structure evolution in magnetic topological materials Show/Hide Abstract The discovery of topological insulators (TIs) has prompted intensive theoretical and experimental studies on realizing various topological states in quantum materials. Owing to the bulk-boundary correspondence, the TIs support conducting surface states that lie within the gapped bulk electronic spectrum of the TIs. These surface states are spin polarized and disperse linearly with Dirac-cone energy dispersion. Constraints of the time-reversal symmetry protect the surface states from backscattering and localization in the presence of nonmagnetic perturbations thereby making TIs promising for low-power energy-efficient quantum electronic applications. Recently, new types of topological materials inspired by magnetism have attracted intensive research interest. In this talk, I will discuss electronic structure evolution across the magnetic transition temperature for rare-earth monopnictide based materials and kagome magnets. Our study indicates that magnetism plays an intricate role in the electronic structure of the topological material family.
|
||||||
|
Date/Time: |
Abstract Number: ANPA2022_0166 Presenting Author: Milo Sprague Presenter's Affiliation: University of Central Florida Title: Novel Electronic Structure Signature across Antiferromagnetic Transition in Rare Earth Monopnictide NdSb Show/Hide Abstract Rare Earth Monopnictides (REM) are a family of materials that have drawn interest for their possession of topological Dirac behavior and magnetic ordering. Band dispersion and Fermi surface mapping across the paramagnetic to antiferromagnetic phase transition in the REM NdSb was obtained through Angle-Resolved Photoemission Spectroscopy and compared with first-principles density functional theory calculations. Predicted features of the density functional theory calculations are found to be present in the ARPES spectrum, however we have also observed fermi arc states below the antiferromagnetic transition that are absent in the DFT. These observations append the list of complex many-body effects associated with magnetic ordering.
|
||||||
|
Date/Time: |
Abstract Number: ANPA2022_0167 Presenting Author: Gyanendra Dhakal Presenter's Affiliation: University of Central Florida Title: Observation of anisotropic Dirac cones in topologically rich Ti2Te2P Show/Hide Abstract Anisotropic bulk Dirac (or Weyl) cones in three dimensional systems have recently gained intense
research interest as they are examples of materials with tilted Dirac (or Weyl) cones indicating
the violation of Lorentz invariance. In contrast, the studies on anisotropic surface Dirac cones
in topological materials which contribute to ansiotropic carrier mobility have been limited. By
employing angle-resolved photoemission spectroscopy and first-principles calculations, we reveal the
anisotropic surface Dirac dispersion in a tetradymite material Ti2Te2P on the (001) plane of the
Brillioun zone. We observe the quasi-elliptical Fermi pockets at the M -point of the Brillouin zone
forming the anisotropic surface Dirac cones. Our calculations of the Z2 indices confirm that the
system is topologically non-trivial with multiple topological phases in the same material. In addition, observed nodalline like features formed by bulk bands make this system topologically rich.
|
||||||
|
Date/Time: |
Abstract Number: ANPA2022_0168 Presenting Author: Dipendra Banjara Presenter's Affiliation: Louisiana State University Title: First-principles simulations of liquid iron-heavy element alloys at high pressure?? Show/Hide Abstract Iron-rich metallic liquid is thought to contain many elements under Earth�s core conditions. While the incorporation of light elements has been studied extensively, our knowledge about liquid iron-heavy element mixtures is limited. Here we investigate the structural and dynamical behavior of four siderophile elements, namely Co, Ni, Mo, and W dissolved in liquid iron using first principles molecular dynamics over wide ranges of pressure (up to 380 GPa) and temperatures (4000 to 7000 K). The calculated pressure-volume-temperature results of these iron-rich alloys are accurately described by adding the appropriative terms to the equation of state of pure iron liquid to account for the effects of temperature and impurity. The simulation results show that the bulk modulus remains almost unaffected by the added impurities while Mo and W increase the melt density much more than Co and Ni mainly due to their heavier mass. To explain the density and seismic velocity profiles of the outer core, light elements like H and C must be added to liquid iron alloys in large amounts. The calculated mean iron coordination number of each of four heavy elements considered is somewhat larger than the mean Fe-Fe coordination number. This suggests that their incorporation is of substitutional nature unlike interstitial mechanism for H and C. The lack of clustering activity, and intra-species interactions of these heavy impurity atoms suggest they are soluble in liquid iron. The diffusion rates of these impurities are found to be comparable to that of host atoms, but they are much lower than those of light elements.
|
||||||
|
Date/Time: |
Abstract Number: ANPA2022_0169 Presenting Author: Robert Smith Presenter's Affiliation: University of Central Florida Title: Unusual magnetic and transport properties in HoMn6Sn6 kagome magnet Show/Hide Abstract With intricate lattice structures, kagome materials are an excellent platform to study various fascinating topological quantum states. In particular, kagome materials, revealing large responses to external stimuli such as pressure or magnetic field, are subject to special investigation. Here, we study the kagome-net HoMn6Sn6 magnet that undergoes paramagnetic to ferrimagnetic transition (below 376 K) and reveals spin-reorientation transition below 200 K. In this compound, we observe the topological Hall effect and substantial contribution of anomalous Hall effect above 100 K. We unveil the pressure effects on magnetic ordering at a low magnetic field from the pressure tunable magnetization measurement. By utilizing high-resolution angle-resolved photoemission spectroscopy, Dirac-like dispersion at the high-symmetry point K is revealed in the vicinity of the Fermi level, which is well supported by the first-principles calculations, suggesting a possible Chern-gapped Dirac cone in this compound. Our investigation will pave the way to understand the magneto-transport and electronic properties of various rare-earth-based kagome magnets.
|
||||||
|
Date/Time: |
Abstract Number: ANPA2022_0170 Presenting Author: Hari Bhandari Presenter's Affiliation: Graduate Student, George Mason University Title: Tuning of Magnetism via Doping in Kagome Magnet YMn6Sn6-xGex Show/Hide Abstract Kagome lattice magnets are an interesting class of materials as they can host topological
properties in their magnetic and electronic structures. YMn6Sn6 is one such compound in which a series of competing magnetic phases is stabilized by applied magnetic field, and both an enigmatic topological Hall effect and a Dirac crossing close to the Fermi energy have been realized. This material also shows a magnetization induced Lifshitz transition and evidence of an efficient charge-spin coupling in one of the magnetic phases, namely the fan-like phase. Tuning the magnetism, and thus the interplay with the electronic states, opens new avenues into precise control of these novel properties. Here, we demonstrate the extreme sensitivity of the magnetic phases in YMn6Sn6-xGex via magnetization and magnetotransport measurements. The high degree of sensitivity to small doping concentrations provides great potential for engineering the magnetic phases and associated electronic properties in this family of rare-earth kagome magnets.
|
||||||
|
Date/Time: |
Abstract Number: ANPA2022_0171 Presenting Author: Yangyang Liu Presenter's Affiliation: University of Central Florida Title: Ultrafast relaxation of acoustic and optical phonons in a topological nodal-line semimetal ZrSiS Show/Hide Abstract Recently, nodalline semimetals based on ZrSiS-family have garnered massive research interests contributing numerous experimental and theoretical works. Despite being the most studied nodal-line semimetal, a clear understanding of the transient state relaxation dynamics and the underlying mechanism in ZrSiS is lacking. Using time- and angle-resolved photoemission spectroscopy, we study the ultrafast relaxation dynamics in ZrSiS and reveal a unique relaxation in the bulk nodalline state which is well-captured by a simple model based on optical and acoustic phonon cooling. Our model predicts linear decay processes for both optical and acoustic phonon relaxations with optical cooling dominant at higher temperatures. Our results reveal different decay mechanisms for the bulk and surface states and pave a way to understand the mechanism of conduction in this material.
|
||||||
|
Date/Time: |
Abstract Number: ANPA2022_0172 Presenting Author: Dr. Anup Pradhan Sakhya Presenter's Affiliation: University of Central Florida Title: Observation of Fermi-arcs and Weyl nodes in a new non-centrosymmetric magnetic Weyl semimetal Show/Hide Abstract Weyl semimetal (WSM), a novel state of quantum matter, hosts Weyl fermions as emergent quasiparticles resulting from the breaking of either inversion or time-reversal symmetry. Magnetic WSMs that arise from broken time-reversal symmetry provide an exceptional platform to understand the interplay between magnetic order and Weyl physics, but few WSMs have been realized. Here, we identify CeAlSi as a new non-centrosymmetric magnetic WSM via angle-resolved photoemission spectroscopy (ARPES) and first-principles density-functional theory-based calculations. Our surface-sensitive vacuum ultraviolet ARPES data confirms the presence of surface Fermi arcs as the smoking gun evidence for the existence of the Weyl semimetallic state in CeAlSi. We also observe bulk Weyl cones in CeAlSi using bulk-sensitive soft-X-ray ARPES measurements. In addition, Ce 4f flat bands are found near the Fermi level, indicating that CeAlSi is a unique platform for investigating exotic quantum phenomena resulting from the interaction of topology, magnetism, and electronic correlations.
|
||||||
|
Date/Time: |
Abstract Number: ANPA2022_0173 Presenting Author: Ganesh Pokharel Presenter's Affiliation: University of California Santa Barbara Title: Evolution of field-induced and impurity-induced magnetic order in the quantum spin liquid candidate NaYbSe2 Show/Hide Abstract Two-dimensional triangular-lattices of rare-earth ions with effective spin-1/2 local moments are perfect candidates for the investigation of the physics of magnetic frustration in the presence of strong quantum fluctuations. The existence of natively fluctuating magnetic ground states manipulate are of interest due to their potential applications in data storage and quantum computing devices, and a key means of understanding these quantum spin liquid states is to perturb the state and induce long-range magnetic order. Here we present the evolution of long-range order magnetic order in the quantum spin liquid candidate NaYbSe2 by the application of both an external magnetic field and through the introduction of non-magnetic Lu impurities. The substitution of Lu3+-ions in the triangular lattice network should dilute the competing interactions, between Yb3+-ions, responsible for the QSL state and induce magnetic order at finite temperature. The nature of nearby field-driven magnetic order and its ability to be stabilized via impurity substitution will be discussed.
|
||||||
|
Date/Time: |
Abstract Number: ANPA2022_0174 Presenting Author: Raj K. Rai Presenter's Affiliation: Central Department of Physics, Tribhuvan University, Nepal. Title: NUMERICAL ANALYTIC CONTINUATION TO PROBE THE ELECTRONIC STRUCTURE OF STRONGLY CORRELATED SYSTEM: MAXIMUM ENTROPY MODEL Show/Hide Abstract We present a mathematical tool to extract the realistic physical information of interacting strongly correlated systems obtained through Quantum Monte Carlo (QMC) simulations. The data obtained through QMC in imaginary time or frequency is not straightforward for obtaining physical observables.
The real frequency spectral function, A(?) from the Green�s function, G(?i??_? ) is an ill-posed problem due to the large conditional number of the kernel matrix. The small noise in G(?i??_? ) can lead to large fluctuations in A(?) and hence to solve this optimization problem efficiently, we use the Maximum Entropy Model (MEM) based on Bayesian statistical rule.
In this study, the Maximum Entropy Model is used to investigate the Mott-Hubbard type metal�insulator transition (MIT) along with the optically induced transport behaviour of the system.
Key words: Double perovskites, DMFT, GGA, Analytic Continuation, Maximum Entropy model
References:
[1] E. Gull, A. J. Millis, A. I. Lichtenstein, A. N. Rubtsov, M. Troyer, and P. Werner,
Continuous-time Monte Carlo methods for quantum impurity models, Rev. Mod.
Phys. 83, 349 (2011).
[2] M. Jarrell and J. Gubernatis, Phys. Rep. 269, 133 (1996).
[3] D. Bergeron, D. and Tremblay, A.M.,. Algorithms for optimized maximum
entropy and diagnostic tools for analytic continuation. Physical Review E, 94(2),
p.023303(2016).
[4] H. L. Feng, S. Calder, M.P. Ghimire, Y.H. Yuan, Y. Shirako, and et. al.
Ba2NiOsO6: A Dirac-Mott insulator with ferromagnetism near 100 K.
Physical Review B, 94(23), p.235158 (2016).
[5] Samanta, K. and Saha-Dasgupta, T. Comparative Study of Electronic Structure
and Magnetic Properties of Osmate Double Perovskites: Ca2FeOsO6 versus
Ca2Co (Ni)OsO6. Journal of the Physical Society of Japan, 87(4),
p.041007 (2018).
|
||||||
Stay Tuned