Strong anomalous proximity effect from spin-singlet superconductors

Satoshi Ikegaya,Yasuhiro Asano,Jaechul Lee,Andreas P Schnyder

doi:10.1103/physrevb.104.l020502

Abstract

The proximity effect from a spin-triplet $p_x$-wave superconductor to a dirty normal-metal has been shown to result in various unusual electromagnetic properties, reflecting a cooperative relation between topologically protected zero-energy quasiparticles and odd-frequency Cooper pairs. However, because of a lack of candidate materials for spin-triplet $p_x$-wave superconductors, observing this effect has been difficult. In this paper, we demonstrate that the anomalous proximity effect, which is essentially equivalent to that of a spin-triplet $p_x$-wave superconductor, can occur in a semiconductor/high-$T_c$ cuprate superconductor hybrid device in which two potentials coexist: a spin-singlet $d$-wave pair potential and a spin--orbit coupling potential sustaining the persistent spin-helix state. As a result, we propose an alternative and promising route to observe the anomalous proximity effect related to the profound nature of topologically protected quasiparticles and odd-frequency Cooper pairs.

Highlights

When a superconductor (SC) is attached to a normal-metal, Cooper pairs (CPs) penetrate into the attached normal segment and modify the electromagnetic properties there
We demonstrate that the anomalous proximity effect, which is essentially equivalent to that of a spin-triplet px-wave superconductor, can occur in a semiconductor/high-Tc cuprate superconductor hybrid device in which two potentials coexist: A spin-singlet d-wave pair potential and a spin-orbit coupling potential sustaining the persistent spin-helix state
We propose an alternative and promising route to observe the anomalous proximity effect related to the profound nature of topologically protected quasiparticles and odd-frequency Cooper pairs

Summary

INTRODUCTION

When a superconductor (SC) is attached to a normal-metal, Cooper pairs (CPs) penetrate into the attached normal segment and modify the electromagnetic properties there. It has been shown that the ZESs penetrated from a spin-triplet px wave are accompanied by odd-frequency CPs [16,17,18,19,20,21], which are responsible for the paramagnetic response in the DN [9,22,23,24,25]. The APE is a remarkable phenomenon related to the intrinsic natures of topologically protected zero-energy quasiparticles and odd-frequency CPs. experimental observations of this effect are an important topic in the physics of superconductivity. Experimentally realizing these models is challenging because strong Zeeman potentials that exceed the superconducting pair potentials are needed to induce effective px-wave superconductivity To resolve this stalemate, in this Letter, we explore an alternative route to observing the APE. We assume a proximity-induced spin-singlet dxy-wave pair potential for the segment above the high-Tc cuprate SC. The proximity-induced spin-singlet dxy-wave pair potential is given by. We assume zero temperature in the following calculations

Anomalous proximity effect

Index theorem

DISCUSSION