Electron-electron interactions in non-equilibrium bilayer graphene

TL;DR

This paper investigates how electron-electron interactions affect the steady-state properties of doped bilayer graphene, revealing their negligible impact on conductivity due to strong interlayer tunneling and unique pseudospin structure.

Contribution

It provides a self-consistent, exact analysis of electron-electron interactions in non-equilibrium bilayer graphene using quantum Liouville and Hartree-Fock methods.

Findings

Interactions have negligible effect on conductivity at zero temperature.

Pseudospin polarization is renormalized by interactions but remains weak.

The influence of interactions is weaker than in single-layer graphene or topological insulators.

Abstract

Conducting steady-states of doped bilayer graphene have a non-zero sublattice pseudospin polarization. Electron-electron interactions renormalize this polarization even at zero temperature, when the phase space for electron-electron scattering vanishes. We show that because of the strength of interlayer tunneling, electron-electron interactions nevertheless have a negligible influence on the conductivity which vanishes as the carrier number density goes to zero. The influence of interactions is qualitatively weaker than in the comparable cases of single-layer graphene or topological insulators, because the momentum-space layer pseudospin vorticity is 2 rather than 1. Our study relies on the quantum Liouville equation in the first Born approximation with respect to the scattering potential, with electron-electron interactions taken into account self-consistently in the Hartree-Fock approximation and screening in the random phase approximation. Within this framework the result we obtain is exact.