Vanishing bulk heat flow in the nu=0 quantum Hall ferromagnet in monolayer graphene

TL;DR

This study investigates the bulk thermal transport in the $ u=0$ quantum Hall ferromagnet in monolayer graphene, revealing unexpectedly vanishing heat flow that challenges existing theoretical predictions about its ground state.

Contribution

The paper provides the first experimental measurement of bulk thermal transport in the $ u=0$ state, showing a discrepancy with theoretical models and prompting further research.

Findings

Bulk thermal transport vanishes at $ u=0$ in graphene.

Contradicts theoretical predictions of finite thermal conductance.

Highlights the need for revised understanding of the ground state.

Abstract

Under high perpendicular magnetic field and at low temperatures, graphene develops an insulating state at the charge neutrality point. This state, dubbed $\nu=0$, is due to the interplay between electronic interactions and the four-fold spin and valley degeneracies in the flat band formed by the $n=0$ Landau level. Determining the ground state of $\nu=0$, including its spin and valley polarization, has been a theoretical and experimental undertaking for almost two decades. Here, we present experiments probing the bulk thermal transport properties of monolayer graphene at $\nu=0$, which directly probe its ground state and collective excitations. We observe a vanishing bulk thermal transport, in contradiction with the expected ground state, predicted to have a finite thermal conductance even at very low temperature. Our result highlight the need for further investigations on the nature of $\nu=0$.