Electronic correlation in Kagome metals and its consequences

Ramakanta Chapai, PhD
Argonne National Laboratory
Date: Jan 20, 2024
Time: 8:30 PM ET

Metallic materials with a Kagome lattice have emerged as a new frontier in condensed matter physics in recent years. Key features in their electronic band structure include Dirac points, van Hove singularities (VHS), and flat bands. In this talk, I will discuss some insightful cases of a Kagome superconductor CsV3Sb5 (CVS), where a complex interplay exists between superconductivity, charge density wave (CDW), and a non-trivial topology. Through the measurement of magnetic quantum oscillations, we have identified the fundamental ‘building blocks’ of the reconstructed Fermi surface, comprising ‘hyperbolic hexagon’ and ‘triangular’ pockets within the CDW state in CVS. These pockets are characterized by sharp corners and strong variations of the Fermi velocity, arising from the proximity to the VHS. I will demonstrate that the observed unconventional transport behavior, such as non-monotonous magnetoresistance and apparent anomalous Hall effect, can, in a semi-quantitative way, be accounted for by the reconstructed Fermi surface structure. As I conclude the talk, I will briefly discuss anomalous features observed in the temperature dependence of upper critical field Hc2(T) of CVS and propose an explanation based on the Fermi surface reconstruction.