Large Rashba unidirectional magnetoresistance in the Fe/Ge(111) interface states

TL;DR

This study demonstrates large Rashba-induced unidirectional magnetoresistance at the Fe/Ge(111) interface, revealing significant spin-orbit effects that can be exploited for spintronic applications.

Contribution

It provides experimental evidence of Rashba states at the Fe/Ge(111) interface through magnetotransport measurements, highlighting a large unidirectional magnetoresistance.

Findings

Unidirectional magnetoresistance up to 0.1% observed.

Rashba energy splitting exceeds that of pure Ge(111) subsurface states.

Temperature dependence indicates strong Rashba effects.

Abstract

The structure inversion asymmetry at surfaces and interfaces give rise to the Rashba spin-orbit interaction (SOI), that breaks the spin degeneracy of surface or interface states. Hence, when an electric current runs through a surface or interface, this Rashba effect generates an effective magnetic field acting on the electron spin. This provides an additional tool to manipulate the spin state in materials such as Si and Ge that, in their bulk form, possess inversion symmetry (or lack structural inersion asymmetry). The existence of Rashba states could be demonstrated by photoemission spectroscopy at the interface between different metals and Ge(111) and by spin-charge conversion experiments at the Fe/Ge(111) interface even though made of two light elements. In this work, we identify the fingerprint of the Rashba states at the Fe/Ge(111) interface by magnetotransport measurements in the form of a large unidirectional magnetoresistance of up to 0.1 \%. From its temperature dependence, we find that the Rashba energy splitting is larger than in pure Ge(111) subsurface states.