Absence of heat flow in {\nu} = 0 quantum Hall ferromagnet in bilayer graphene

TL;DR

This study investigates the thermal transport properties of the { u} = 0 quantum Hall state in bilayer graphene, revealing an unexpected absence of heat flow despite theoretical predictions of finite thermal conductance.

Contribution

The paper provides experimental evidence that challenges existing theories by showing no detectable thermal conductance in the { u} = 0 state, suggesting gapped excitations.

Findings

No measurable thermal conductance detected.

Evidence of gapped collective excitations.

Highlights need for further research into the { u} = 0 state.

Abstract

The charge neutrality point of bilayer graphene, denoted as {\nu} = 0 state, manifests competing phases marked by spontaneously broken isospin (spin/valley/layer) symmetries under external magnetic and electric fields. However, due to their electrically insulating nature, identifying these phases through electrical conductance measurements remains challenging. A recent theoretical proposal introduces a novel approach, employing thermal transport measurements to detect these competing phases. Here, we experimentally explore the bulk thermal transport of the {\nu} = 0 state in bilayer graphene to investigate its ground states and collective excitations associated with isospin. While the theory anticipates a finite thermal conductance in the {\nu} = 0 state, our findings unveil an absence of detectable thermal conductance. Through variations in the external electric field and temperature-dependent measurements, our results suggest towards gapped collective excitations at {\nu} = 0 state. Our findings underscore the necessity for further investigations into the nature of {\nu} = 0.