Universal quantized thermal conductance in graphene

Abstract

The universal quantization of thermal conductance provides information on a state's topological order. Recent measurements revealed that the observed value of thermal conductance of the <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML"> <mml:mrow> <mml:mrow><mml:mfrac><mml:mn>5</mml:mn> <mml:mn>2</mml:mn></mml:mfrac> </mml:mrow> </mml:mrow> </mml:math> state is inconsistent with either Pfaffian or anti-Pfaffian model, motivating several theoretical articles. Analysis has been made complicated by the presence of counter-propagating edge channels arising from edge reconstruction, an inevitable consequence of separating the dopant layer from the GaAs quantum well and the resulting soft confining potential. Here, we measured thermal conductance in graphene with atomically sharp confining potential by using sensitive noise thermometry on hexagonal boron-nitride encapsulated graphene devices, gated by either SiO₂/Si or graphite back gate. We find the quantization of thermal conductance within 5% accuracy for ν = <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML"> <mml:mrow><mml:mrow><mml:mn>1</mml:mn> <mml:mo>;</mml:mo> <mml:mfrac><mml:mn>4</mml:mn> <mml:mn>3</mml:mn></mml:mfrac> <mml:mo>;</mml:mo> <mml:mn>2</mml:mn></mml:mrow> </mml:mrow> </mml:math> and 6 plateaus, emphasizing the universality of flow of information. These graphene quantum Hall thermal transport measurements will allow new insight into exotic systems like even-denominator quantum Hall fractions in graphene.