Cascades in transport and optical conductivity of Twisted Bilayer Graphene

TL;DR

This study uses DMFT+H calculations to analyze transport and optical properties of twisted bilayer graphene, revealing resistive states, doping-dependent Drude behavior, and cascade features in optical conductivity.

Contribution

It introduces a combined DMFT+H approach to uncover detailed transport and optical phenomena in TBG, emphasizing the role of itinerant electrons and cascade effects.

Findings

Resistive states around integer fillings resemble experimental observations.

Doping-dependent Drude weight and scattering rate with resets at integers.

Optical conductivity shows cascade features with asymmetric intensity resets.

Abstract

Using a combined Dynamical Mean Field Theory and Hartree (DMFT+H) calculation we study the transport and optical properties of the 8-band heavy fermion model for Twisted Bilayer Graphene (TBG) in the normal state. We find resistive states around integer fillings which resemble the ones observed in transport experiments. From a Drude fitting of the low frequency optical conductivity, we extract a very strongly doping-dependent Drude weight and scattering rate, resetting at the integers. For most dopings, particularly above the integers, the Drude scattering rate is high but notably smaller than that of the local electrons. This highlights the important role of itinerant electrons in the transport properties, despite their limited spectral weight on the flat bands. At far infrared frequencies, the optical conductivity exhibits cascades characterized by highly asymmetric resets of the intensity and oscillations in the interband peak frequencies.