Absence of heat flow in ν = 0 quantum Hall ferromagnet in bilayer graphene

Ravi Kumar; Saurabh Kumar Srivastav; Ujjal Roy; Ujjawal Singhal; K. Watanabe; T. Taniguchi; Vibhor Singh; P. Roulleau; Anindya Das

doi:10.1038/s41567-024-02673-z

Journal article Absence of heat flow in ν = 0 quantum Hall ferromagnet in bilayer graphene

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Ravi Kumar, Saurabh Kumar Srivastav, Ujjal Roy, Ujjawal Singhal, K. Watanabe, T. Taniguchi, Vibhor Singh, P. Roulleau, Anindya Das. Absence of heat flow in ν = 0 quantum Hall ferromagnet in bilayer graphene. Nature Physics. 2024, 20 (12), 1941-1947. https://doi.org/10.1038/s41567-024-02673-z

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The charge neutrality point of bilayer graphene, denoted as ν = 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 ν = 0 state in bilayer graphene to investi- gate its ground states and collective excitations associated with isospin. While the theory anticipates a finite thermal conductance in the ν = 0 state, our findings unveil an absence of detectable thermal con- ductance. Through variations in the external electric field and temperature-dependent measurements, our results suggest towards gapped collective excitations at ν = 0 state. Our findings underscore the necessity for further investigations into the nature of ν = 0.

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