Tunneling spectroscopy and Majorana modes emergent from topological gapless phases in high-Tc cuprate superconductors

TL;DR

This paper predicts that high-Tc cuprate superconductors can host Majorana modes due to topological gapless phases induced by spin-orbit interactions, which could be observed via tunneling spectroscopy and related experiments.

Contribution

It demonstrates the emergence of Majorana modes in high-Tc cuprates through topological gapless phases driven by spin-orbit interactions and predicts observable tunneling signatures.

Findings

Majorana modes cause zero-bias conductance plateaus

Split nodal points lead to robust Majorana edge states

Experimental signatures include 4π periodicity and flux quanta in tricrystal experiments

Abstract

We explore possible signatures for observing Majorana Fermions in the tunneling spectroscopy of high-Tc cuprate superconductors. We find that as long as the Rashba spin orbit interaction is in presence either through proximity effect due to an electrode made by heavy metal or by the intrinsic nature of cuprates, in addition to the Heisenberg spin exchange interaction, the Dzyaloshinskii-Moriya and spin dipole-dipole interactions are induced. As a result, $p$-wave superconductivity is induced with the gap function $d$-vector being not aligned with the internal magnetic field of the spin-orbit interaction. Most importantly, the ground state goes through transitions into gapless phases with split nodal points. The split nodal structure always results in Majorana modes for any interfaces that are not exactly in (100) or (010) directions. Hence for general interfaces, existence of Majorana bound edge states is a robust feature. Our results indicate that these Majorana modes would result in a small plateau in tunneling spectrum near zero bias peak and in 4 $\pi$ periodicity in typical SIS$'$ junctions . As a result, it is easy for a $\pi$-ring in tricrystal experiments to hold Majorana Ferimions and exhibit periods of two flux quanta in external magnetic fields. These phenomena may have been already observed in experiments and their connections to experimental results are discussed.