Onset of an Insulating Zero-Plateau Quantum Hall State in Graphene

TL;DR

This paper models the dissipative conductance in the zero-plateau quantum Hall state in graphene, revealing a transition from metallic to insulating behavior driven by interactions and magnetic domain walls, aligning with recent experimental observations.

Contribution

It introduces a theoretical framework describing how magnetic domain walls and interactions lead to a metal-insulator transition in graphene's quantum Hall state.

Findings

Finite resistivity R_{xx} due to spin-flip backscattering

Crossover from metallic to insulating behavior with temperature

Divergence of R_{xx} as interaction parameter approaches critical value

Abstract

We analyze the dissipative conductance of the zero-plateau quantum Hall state appearing in undoped graphene in strong magnetic fields. Charge transport in this state is assumed to be carried by a magnetic domain wall, which forms by hybridization of two counter--propagating edge states of opposing spin due to interactions. The resulting non--chiral edge mode is a Luttinger liquid of parameter K, which enters a gapped, perfectly conducting state below a critical value K_c\approx 1/2. Backscattering in this system involves spin flip, so that interaction with localized magnetic moments generates a finite resistivity R_{xx} via a "chiral Kondo effect". At finite temperatures T, R_{xx}(T) exhibits a crossover from metallic to insulating behavior as K is tuned across a threshold K_{MI}. For T->0, R_{xx} in the intermediate regime K_{MI}<K<K_c is finite, but diverges as K approaches K_c. This model provides a natural interpretation of recent experiments.