Interaction-Enhanced Topological Hall Effects in Strained Twisted Bilayer Graphene

TL;DR

This paper investigates how electron-electron interactions influence topological Hall effects in strained twisted bilayer graphene aligned with hBN, revealing significant modifications to topological transport properties due to Coulomb interactions.

Contribution

It provides a detailed analysis of interaction-induced changes in Berry curvature distribution and Hall conductivities in TBG/hBN, highlighting the role of electron-electron interactions in topological phenomena.

Findings

Remote bands significantly contribute to Hall currents at certain fillings.

Electron-electron interactions strongly renormalize band structure and topological properties.

Topological transport is substantially modified by Coulomb interactions, explaining recent experiments.

Abstract

We analyze the effects of the long-range Coulomb interaction on the distribution of Berry curvature among the bands near charge neutrality of twisted bilayer graphene (TBG) closely aligned with hexagonal boron nitride (hBN). Due to the suppressed dispersion of the narrow bands, the band structure is strongly renormalized by electron-electron interactions, and thus, the associated topological properties of the bands are sensitive to filling. Using a Hartree formalism, we calculate the linear and nonlinear Hall conductivities, and find that for certain fillings, the remote bands contribute substantially to the Hall currents while the contribution from the central bands is suppressed. In particular, we find that these currents are generically substantial near regions of energies where the bands are highly entangled with each other, often featuring doping-induced band inversions. Our results demonstrate that topological transport in TBG/hBN is substantially modified by electron-electron interactions, which offer a simple explanation to recent experimental results.