Majorana Kramers Doublets in $d_{x^2-y^2}$-wave Superconductors with Rashba Spin-Orbit Coupling

TL;DR

This paper demonstrates that a quasi-one-dimensional $d_{x^2-y^2}$-wave superconductor with Rashba spin-orbit coupling can host Majorana Kramers Doublets, which are protected by time-reversal symmetry and have distinctive experimental signatures.

Contribution

It reveals that such superconductors are topological DIII class systems supporting Majorana Kramers Doublets, a novel state protected by time-reversal symmetry.

Findings

Majorana Kramers Doublets exist at each end of the superconductor.

Breaking time-reversal symmetry leads to single Majorana end states.

Resonant Andreev reflection produces a zero-bias conductance peak of 4e^2/h.

Abstract

In this work, we show that a quasi-one-dimensional $d_{x^2-y^2}$-wave superconductor with Rashba spin-orbit coupling is a DIII class, time-reversal invariant, topological superconductor (TS) which supports a Majorana Kramers Doublet (MKD) at each end of the TS. A MKD is a pair of Majorana end states (MESs) protected by time-reversal symmetry (TRS). An external magnetic field breaks TRS and drives the system from DIII to D class in which case a single MES appears at each end of the TS. We show that a MKD induces resonant Andreev reflection with zero bias conductance peak of $4e^2/h$. Experimental realizations of the proposed model are discussed.