Transport Signatures of Radial Rashba Spin-Orbit Coupling at Ferromagnet/Superconductor Interfaces

TL;DR

This paper investigates how radial Rashba spin-orbit coupling at ferromagnet/superconductor interfaces affects tunneling conductance and Hall effects, proposing a method to experimentally measure the Rashba angle in twisted multilayer systems.

Contribution

It introduces a theoretical framework to detect radial Rashba SOC via magnetization-angle shifts in tunneling conductance and Hall measurements.

Findings

Radial Rashba SOC causes measurable shifts in magnetization-angle-dependent conductance.

The Rashba angle $\theta_R$ can be extracted from experimental magnetization-angle shifts.

Radial Rashba SOC effects are significant in twisted multilayer heterostructures.

Abstract

Spin-orbit coupling (SOC) emerging at the interfaces of superconducting magnetic tunnel junctions is at the heart of multiple unprecedented physical phenomena, covering triplet proximity effects induced by unconventional (spin-flip) Andreev reflections, giant transport magnetoanisotropies, sizable tunneling anomalous Hall effects, and electrically controlled current-reversing $ 0 $--$ \pi $(-like) transitions in Josephson contacts. Recent first-principles calculations proposed that the Rashba spin-orbit fields in twisted graphene/transition-metal dichalcogenide and van der Waals multilayers can -- owing to broken mirror symmetries -- exhibit an unconventional radial component (with spin parallel to the electron's momentum), which can be quantified by the Rashba angle $ \theta_\mathrm{R} $. We theoretically explore the ramifications of radial Rashba SOC at the interfaces of vertical ferromagnet/superconductor tunnel junctions with a focus on the magnetoanisotropies of the tunneling and tunneling-anomalous-Hall-effect conductances. Our results demonstrate that $ \theta_\mathrm{R} $ can be experimentally extracted from respective magnetization-angle shifts, providing a robust way to probe the radial Rashba SOC induced by twisted multilayers that are placed as tunneling barriers between ferromagnetic and superconducting electrodes.