Signatures of a Spin-Active Interface and Locally Enhanced Zeeman field in a Superconductor-Chiral Material Heterostructure

TL;DR

This paper investigates how a superconductor-chiral material heterostructure creates a localized, enhanced Zeeman field at the interface, affecting surface superconductivity and inducing spin-polarized Andreev bound states, with potential implications for spintronics.

Contribution

It demonstrates the generation of an enhanced interface Zeeman field through a superconductor-chiral material interface without magnetic elements, revealing new spin-active interface phenomena.

Findings

Enhanced interface Zeeman field selectively closes surface superconducting gap

Induction of spin-polarized Andreev bound states in the heterostructure

Significantly increased effective Landé g-factor (~12) at the interface

Abstract

A localized Zeeman field, intensified at heterostructure interfaces, could play a crucial role in a broad area including spintronics and unconventional superconductors. Conventionally, the generation of a local Zeeman field is achieved through magnetic exchange coupling with a magnetic material. However, magnetic elements often introduce defects, which could weaken or destroy superconductivity. Alternatively, the coupling between a superconductor with strong spin-orbit coupling and a non-magnetic chiral material could serve as a promising approach to generate a spin active interface. In this study, we leverage an interface superconductor, namely induced superconductivity in noble metal surface states, to probe the spin active interface. Our results unveil an enhanced interface Zeeman field, which selectively closes the surface superconducting gap while preserving the bulk superconducting pairing. The chiral material, i.e. trigonal tellurium, also induces Andreev bound states (ABS) exhibiting spin polarization. The field dependence of ABS manifests a substantially enhanced interface Land\'e g-factor (g_eff ~ 12), thereby corroborating the enhanced interface Zeeman energy.