Rotational Isotropy Breaking as Proof for Spin-polarized Cooper Pairs in the Topological Superconductor CuxBi2Se3

TL;DR

This paper proposes a method to identify spin-polarized triplet pairing in the topological superconductor CuxBi2Se3 by detecting anisotropy in thermal conductivity, highlighting the role of spin-orbit coupling and Dirac formalism.

Contribution

It introduces a novel approach to determine pairing symmetry in topological superconductors through angle-dependent thermal conductivity measurements.

Findings

Strong anisotropy in thermal conductivity indicates odd-parity spin-polarized triplet pairing.

Isotropy breaking is explicitly linked to Dirac formalism and spin-orbit coupling.

Classification of gap functions clarifies the origin of anisotropy.

Abstract

In a promising candidate of topological superconductors, CuxBi2Se3, we propose a way to exclusively determine the pairing symmetry. The proposal suggests that the angle dependence of the thermal conductivity in the basal ab-plane shows a distinct strong anisotropy only when the pairing symmetry is an odd-parity spin-polarized triplet below the superconducting transition temperature (Tc). Such striking isotropy breaking below Tc is explicitly involved in Dirac formalism for superconductors, in which the spin-orbit coupling is essential. We classify possible gap functions based on the Dirac formalism and clarify an origin of the isotropy breaking.