SEMINAR 2022

Abstract

The most recognizable feature of graphene’s electronic spectrum is its Dirac point around which interesting phenomena tend to cluster. At elevated temperatures thermal excitations can overcome the disorder and create an electron-hole (e-h) plasma of Dirac fermions. The Dirac plasma has recently been found to exhibit unusual properties including quantum critical conductivity and hydrodynamic flow.

First, I’ll discuss our recent work on magnetotransport properties of Dirac plasma in graphene. In low magnetic field, the plasma exhibits giant magnetoresistivity reaching >100% in 0.1 T even at room temperature. This is orders of magnitude higher than magnetoresistivity found in any other system at such temperatures and originates from the exceptional mobility of graphene at the neutrality point. With the onset of Landau quantization in a few T, where the e-h plasma resides on the zeroth Landau level, giant linear magnetoresistivity emerges which is sensitive to the Columb interaction in the system.

In the second part of my talk I’ll duscuss the out-of-equillibrium transport in twited bilayer graphene and other graphene superlattices which is, surprisunaly, closely related to the Dirac plasma. Due to small number of carriers and reduced Fermi velocity, even moderate current bias in those systems produces a strong shift of Fermi surface. That leads to the current-critical behavior with superconducting-like IV curves. Criticalities develop when the drift velocity of electrons flow approach the Fermi velocity of the system. The observed anomaly caused by the Schwinger-like production of electron-hole plasma. The observed behavior is expected to be common for all 2D superlattices.