Spontaneous Layer Polarization and Conducting Domain Walls in the Quantum Hall Regime of Bilayer Graphene

TL;DR

This paper investigates how domain walls between different symmetry-broken phases in bilayer graphene under magnetic and electric fields can host conducting edge states, explaining conductance enhancements at phase transitions.

Contribution

It proposes a criterion for the existence of conducting edge states at domain walls and analyzes how lattice interactions favor layer polarized states.

Findings

Conducting edge states appear at domain walls between different phases.

Lattice interactions can stabilize spontaneously layer polarized states.

Enhanced conductance at phase transitions is due to these edge states.

Abstract

Bilayer graphene subjected to perpendicular magnetic and electric fields displays a subtle competition between different symmetry broken phases, resulting from an interplay between the internal spin and valley degrees of freedom. The transition between different phases is often identified by an enhancement of the conductance. Here, we propose that the enhanced conductance at the transition is due to the appearance of robust conducting edge states at domain walls between the two phases. We formulate a criterion for the existence of such conducting edge states at the domain walls. For example, for a spontaneously layer polarized state at filling factor $\nu=2$, domain walls between regions of opposite polarization carry conducting edge modes. A microscopic analysis shows that lattice-scale interactions can favor such a layer polarized state.