Topological Majorana zero modes and the superconducting diode effect driven by Fulde-Ferrell-Larkin-Ovchinnikov pairing in a helical Shiba chain

TL;DR

This paper presents a theoretical study showing how FFLO pairing in a helical Shiba chain can host Majorana zero modes and induce a superconducting diode effect by breaking time-reversal and inversion symmetries.

Contribution

It introduces a self-consistent BdG formalism to analyze FFLO pairing in helical Shiba chains, revealing its role in topological MZMs and non-reciprocal charge transport.

Findings

FFLO pairing supports topological Majorana zero modes at chain ends

FFLO state induces superconducting diode effect due to finite Cooper pair momentum

Out-of-plane Zeeman field and helical spin texture are crucial for phenomena

Abstract

We propose a theoretical framework for the realization of Fulde-Ferrell-Larkin-Ovchinnikov (FFLO) pairing in a helical Shiba chain subjected to an out-of-plane Zeeman field, analyzed through a self-consistent Bogoliubov-de-Gennes (BdG) mean-field formalism approach. A chain of magnetic adatoms with helical spin texture deposited on the surface of a common $s$-wave superconductor, has emerged as a pivotal platform for realizing topological Majorana zero modes (MZMs). Our study reveals the crucial role of finite momentum pairing of Cooper pairs in the form of FFLO state which also supports topological MZMs at the ends of the chain. Interestingly, we demonstrate that FFLO pairing facilitates non-reciprocal charge transport, giving rise to superconducting diode effect in our system where both time-reversal and inversion symmetries are broken. Such diode effect stems directly from the presence of finite Cooper pair momentum of the FFLO ground state. Our comprehensive analysis highlights the intricate interplay between the richness of helical Shiba chain, the out-of-plane Zeeman field, and FFLO pairing in the emergence of MZMs and driving the superconducting diode effect. These findings offer valuable insights into the design and realization of topological superconducting devices with diode-like properties, potentially advancing technological applications in quantum computing and superconducting electronics.