# Gauge phonon dominated resistivity in twisted bilayer graphene near magic angle

## TL;DR

This paper demonstrates that in twisted bilayer graphene near the magic angle, resistivity is primarily influenced by charged impurities at low temperatures and gauge phonons at higher temperatures, explaining various experimental observations.

## Contribution

It introduces a comprehensive model showing gauge phonons and charged impurities as dominant scattering mechanisms in tBG near the magic angle, explaining temperature and density-dependent resistivity behaviors.

## Key findings

- Resistivity decreases monotonically with carrier density at low temperature due to impurities.
- Gauge phonons dominate resistivity at higher temperatures, causing weak density dependence.
- Non-monotonic temperature dependence near charge neutrality is predicted and testable.

## Abstract

Recent experiments on twisted bilayer graphene (tBG) close to magic angle show that a small relative rotation in a van der Waals heterostructure greatly alters its electronic properties. We consider various scattering mechanisms and show that the carrier transport in tBG is dominated by a combination of charged impurities and acoustic gauge phonons. Charged impurities still dominate at low temperature and densities because of the inability of Dirac fermions to screen long-range Coulomb potentials at charge neutrality; however, the gauge phonons dominate for most of the experimental regime because although they couple to current, they do not induce charge and are therefore unscreened by the large density of states close to magic angle. We show that the resistivity has a strong monotonically decreasing carrier density dependence at low temperature due to charged impurity scattering, and weak density dependence at high temperature due to gauge phonons. Away from charge neutrality, the resistivity increases with temperature, while it does the opposite close to the Dirac point. A non-monotonic temperature dependence observed only at low temperature and carrier density is a signature of our theory that can be tested in experimentally available samples.