Topological Transition of Graphene from Quantum Hall Metal to Quantum Hall Insulator at $\nu=0$

TL;DR

This paper investigates the transition in graphene from a quantum Hall metal to an insulator at filling factor zero, driven by magnetic field-induced lattice distortions and bond fluctuations, explaining experimental observations.

Contribution

It introduces a model where magnetic field-driven lattice distortions and bond fluctuations cause a topological transition in graphene at $ u=0$, explaining the insulating phase emergence.

Findings

Transition from QH-metal to QH-insulator depends on magnetic field strength.

Critical field varies with bond fluctuation levels.

Cleaner samples exhibit the insulating phase at lower fields.

Abstract

The puzzle of recently observed insulating phase of graphene at filling factor $\nu=0$ in high magnetic field quantum Hall (QH) experiments is investigated. We show that the magnetic field driven Peierls-type lattice distortion (due to the Landau level degeneracy) and random bond fluctuations compete with each other, resulting in a transition from a QH-metal state at relative low field to a QH-insulator state at high enough field at $\nu=0$. The critical field that separates QH-metal from QH-insulator depends on the bond fluctuation. The picture explains well why the field required for observing the insulating phase is lower for a cleaner sample.