Condensed Matter Theory Seminar: Dmytro Pesin - “Linear and Nonlinear Magnetotransport on a Quantum Spin Hall Edge”

Event time: 
Thursday, April 27, 2023 - 1:00pm to 2:00pm
Sloane Physics Laboratory SPL, Room 51 See map
217 Prospect Street
New Haven, CT 06511
Dmytro Pesin - University of Virginia, Charlottesville
Event description: 

Transport and magnetotransport on a helical edge of a quantum spin Hall, or two-dimensional topological insulator, phase have been considered one of the main tests for the identification of this phase. In this talk, I will show that in the presence of bulk midgap states, there is a singular cusp-like contribution to the positive magnetoresistance on a topological edge. It stems from resonant midgap states weakly hybridized with the edge. In the presence of a magnetic field, the midgap energy levels are spin-split, and hybridization of these levels with the itinerant edge states leads to backscattering, and the ensuing increase in the resistance. The singular behavior persists for both coherent and incoherent edge transport regimes. The theory for the incoherent regime appears to describe the experimental observations for the magnetoresistance for monolayer WTe2 at liquid helium temperatures.
I will also discuss nonlinear magnetotransport on a topological edge, focusing on the current which is quadratic in the bias voltage, and odd in the magnetic field. This type of current is in general sensitive to the electron-electron interactions. In monolayer WTe2, the magnitude of the effect can be explained by the current-induced effective Zeeman field on the edge.
Host: Meng Cheng ( & Tyler Ellison (