François Parmentier

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Under high perpendicular magnePc field and at low temperatures, graphene develops an
insulaPng state at the charge neutrality point. This state, dubbed nu=0, is due to the interplay
between electronic interacPons 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 polarizaPon, has been a theorePcal and experimental undertaking for almost two
decades. Here, we present experiments probing the bulk thermal transport properPes of
monolayer graphene at nu=0, which directly probe its ground state and collecPve excitaPons.
We observe a vanishing bulk thermal transport, in contradicPon with the expected ground
state, predicted to have a finite thermal conductance even at very low temperature. Our result
highlight the need for further invesPgaPons on the nature of nu=0.

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Université Paris-Saclay
Seminar Room of the Institute of Physics II
Contact: Erwann Bocquillon