Optimizing one dimensional superconducting diodes: Interplay of Rashba spin-orbit coupling and magnetic fields

TL;DR

This paper investigates how Rashba spin-orbit coupling and magnetic fields influence the superconducting diode effect in nanowire devices, revealing conditions for large diode efficiencies and novel behaviors due to higher-order SOC.

Contribution

It provides a comprehensive analysis of SDE in Rashba nanowires, highlighting the role of linear and higher-order SOC and presenting a phase diagram with emergent FFLO states.

Findings

Rashba nanowires with linear SOC achieve >45% diode efficiency.

Higher-order SOC enables diode effects without longitudinal Zeeman fields.

The phase diagram reveals emergent FFLO superconducting states.

Abstract

The superconducting diode effect (SDE) refers to the non-reciprocal nature of the critical current (maximum current that a superconductor can withstand before turning into a normal metal) of a superconducting device. Here, we investigate SDE in helical superconductors with broken inversion and time-reversal symmetry, focusing on a prototypical Rashba nanowire device proximitized by an s-wave superconductor and subjected to external magnetic fields. Using a self-consistent Bogoliubov-de Gennes mean-field formalism, we analyze the interplay between linear and higher-order spin-orbit coupling (SOC), bulk supercurrents, and external magnetic fields. Our results demonstrate that Rashba nanowires with only linear SOC can achieve incredibly large diode efficiencies > 45% through the interplay of longitudinal and transverse magnetic fields. Notably, higher-order SOC introduces qualitatively different behavior, enabling finite diode efficiency even in the absence of a longitudinal Zeeman field due to inherent energy dispersion asymmetry. We present a comprehensive phase diagram of the device elucidating the emergent Fulde-Ferrell-Larkin-Ovchinnikov (FFLO) superconducting state and demonstrate that proximitized Rashba nanowires offer a versatile, practical platform for SDE, with potential realizations in existing material systems. These results provide crucial insights for optimizing SDE in nanoscale superconducting devices, paving the way for next-generation dissipationless quantum electronics.