Asymmetric Andreev Reflection Induced Electrical and Thermal Hall-like Effects in Metal/Anisotropic Superconductor Junctions

TL;DR

This paper demonstrates that asymmetric Andreev reflection in metal/anistropic superconductor junctions can induce Hall-like electric and thermal effects without magnetic fields, driven by mirror symmetry breaking.

Contribution

It reveals a novel mechanism for Hall-like effects arising from anisotropic superconductors and asymmetric Andreev reflection, independent of magnetic field or time-reversal symmetry breaking.

Findings

Asymmetric Andreev reflection induces transverse electric and thermal currents.

Hall-like effects occur without magnetic fields, due to mirror symmetry breaking.

A transverse thermoelectric effect, similar to the Ettingshausen effect, is identified.

Abstract

By investigating the nonequilibrium transport across a metal/superconductor junction in both nonrelativistic and relativistic cases, we reveal that the asymmetric Andreev reflection with anisotropic superconductors is able to induce the electric and thermal Hall-like effect, in the absence of magnetic field. That is, a longitudinal electric voltage or temperature bias can induce transverse electric or thermal currents merely through the asymmetric Andreev reflection, respectively. In particular, a transverse thermoelectric effect, i.e., the Ettingshausen-like effect, is identified, although the conjugate Nernst effect is absent. The direction change of these electric and thermal Hall-like currents is also discussed. The Hall-like effects uncovered here do not require the conventional time-reversal symmetry breaking, but rather originate from the mirror symmetry breaking with respect to the interface normal due to the anisotropic paring symmetry of the superconductor.