Half-integer quantized thermal conductance plateau in chiral topological superconductor systems

Abstract

We investigate the thermal transport properties of a quantum anomalous Hall insulator nanoribbon covered by superconductors. Due to the peculiar properties of chiral Majorana fermion (CMF) edge states, we found a half-integer quantized thermal conductance plateau. Different from the ordinary superconductor which conducts electricity but does not conduct heat, in the quantum anomalous Hall insulator--topological superconductor junction, the CMF occurs at the boundary of the topological superconductor which carries heat from left to right. A chiral topological superconductor with Chern number $\mathcal{N}=\ifmmode\pm\else\textpm\fi{}1$ has a single CMF, which is equivalent to half an ordinary fermion propagating along the edge, leading to a half-integer quantized thermal conductance plateau. When the topological superconducting edge has two CMFs, it is equivalent to ejecting an ordinary fermion, resulting in an integer quantized thermal conductance plateau. Moreover, the half-integer quantized thermal conductance can also be used to study the properties of Majorana Kramer pairs in a helical topological superconductor. Finally, we also find that the half-integer quantized plateau appears against moderate disorder and with the metal leads besides the quantum anomalous Hall insulator, which is promising to be realized in experiments.