Topological Phases in the Zeroth Landau Level of Bilayer Graphene

TL;DR

This paper investigates the complex quantum Hall phases in bilayer graphene's zeroth Landau level, highlighting the emergence of non-Abelian states at specific filling factors and their theoretical characterization.

Contribution

It provides a detailed analysis of the phase diagram considering realistic interactions, identifying non-Abelian states at =-1/2 and clarifying their nature compared to other candidate states.

Findings

Robust quantum Hall states at multiple filling factors identified.

Evidence that the =-1/2 state is non-Abelian, described by Moore-Read Pfaffian.

Ruling out alternative candidate states like the 331 state.

Abstract

We analyze the phase diagram of the zeroth Landau level of bilayer graphene, taking into account the realistic effects of screening of the Coulomb interaction and the strong mixing between two degenerate sublevels. We identify robust quantum Hall states at filling factors \nu=-1, -4/3, -5/3, -8/5, -1/2, and discuss the nature of their ground states, collective excitations, and relation to the more familiar states in GaAs using a tractable model. In particular, we present evidence that the \nu=-1/2 state, which was recently reported experimentally, is non-Abelian, and described by either the Moore-Read Pfaffian wave function or its particle-hole conjugate, while ruling out other candidates such as the 331 state.