290S/290K Quantum Materials Seminar: Chunli Huang (University of Kentucky); Wednesday, February 7 at 2:00 PM Pacific Time in 402 Physics South
Time/Venue: Wednesday, February 7 at 2:00 PM Pacific Time in 402 Physics South and via Zoom:
https://berkeley.zoom.us/j/99523499113pwd=REovb3pyam03WXQwbEhrU3dqNHZvdz09
Meeting ID: 995 2349 9113 Passcode: 600704
Host: Ehud Altman / Yu-Ping Lin
Title: Landau-Level Mixing and SU(4) Symmetry Breaking in Graphene
Abstract: Recent scanning tunneling microscopy experiments on graphene at charge neutrality under strong magnetic fields have uncovered a ground state characterized by Kekulé distortion (KD). In contrast, non-local spin and charge transport experiments in double-encapsulated graphene, which has a higher dielectric constant, have identified an antiferromagnetic (AF) ground state. We propose a mechanism to reconcile these conflicting observations, by showing that Landau-level mixing can drive a transition from AF to KD with the reduction of the dielectric screening. Our conclusion is drawn from studying the effect of Landau-level mixing on the lattice-scale, valley-dependent interactions to leading order in graphene's fine structure constant. This analysis provides three key insights: 1) Valley-dependent interactions remain predominantly short-range with the m=0 Haldane pseudopotential being at least an order of magnitude greater than the others, affirming the validity of delta-function approximation for these interactions. 2) The phase transition between the AF and KD states is driven by the microscopic process in the double-exchange Feynman diagram. 3) The magnitudes of the coupling constants are significantly boosted by remote Landau levels. Our model also provides a theoretical basis for numerical studies of fractional quantum Hall states in graphene. (https://arxiv.org/abs/2401.12528)
See the Physics Department calendar for future seminars.