Thermal transport in multiple Majorana edge states of hybrid topological superconductor junctions

Abstract

The hybrid topological superconductor (TSC) with multiple Majorana edge states can be formed in a system where a magnetic topological insulator (MTI) thin film is coupled with two s-wave superconductors in proximity. The band structure and thermal transport properties of the hybrid TSC hosting chiral and helical Majorana edge states are investigated. By using the nonequilibrium Green’s function method combined with the Landauer–Büttiker formula, the scattering coefficients (i.e., the normal tunneling T, the local Andreev reflection TLAR, the crossed Andreev reflection TCAR) and two-terminal electric thermal conductance κe are calculated. With the change of the exchange field Mz, the system goes through a series of topological phase transitions. The chiral Majorana edge states, the helical Majorana edge states and the multiple Majorana edge states possessing both chiral and helical edge modes are induced at the boundary of TSC. At the boundary of the central TSC, a single Majorana fermion edge state is equivalent to half an ordinary fermion to carry heat, leading to the generation of a half-integer quantized thermal conductance plateau. Thus, half-integer (i.e., 1/2, 3/2) and integer (i.e., 1, 2) quantized thermal conductance plateaus appear in different topological phases. These quantized plateaus that survive well over a certain range of temperatures can be used experimentally to detect chiral and helical Majorana fermions.