Tuning spin-charge interconversion with quantum confinement in ultrathin Bi/Ge(111) films

TL;DR

This study demonstrates that quantum confinement in ultrathin Bi/Ge(111) films significantly enhances spin-charge interconversion efficiency at room temperature, promising scalable spintronic applications.

Contribution

It reveals how quantum size effects in nanometric Bi islands boost SCI efficiency, combining advanced characterization with direct quantification methods.

Findings

Quantum confinement enhances SCI efficiency in Bi/Ge(111) films.

Room temperature SCI efficiency is significantly increased.

Structural and electronic properties are characterized by XRD, STM, and S-ARPES.

Abstract

Spin-charge interconversion (SCI) phenomena have attracted a growing interest in the field of spintronics as means to detect spin currents or manipulate the magnetization of ferromagnets. The key ingredients to exploit these assets are a large conversion efficiency, the scalability down to the nanometer scale and the integrability with opto-electronic and spintronic devices. Here we show that, when an ultrathin Bi film is epitaxially grown on top of a Ge(111) substrate, quantum size effects arising in nanometric Bi islands drastically boost the SCI efficiency, even at room temperature. Using x-ray diffraction (XRD), scanning tunneling microscopy (STM) and spin- and angle-resolved photoemission (S-ARPES) we obtain a clear picture of the film morphology, crystallography and electronic structure. We then exploit the Rashba-Edelstein effect (REE) and inverse Rashba-Edelstein effect (IREE) to directly quantify the SCI efficiency using optical and electrical spin injection.