Optical manipulation of the Rashba effect in germanium quantum wells

TL;DR

This paper demonstrates optical control of the Rashba effect in germanium quantum wells, showing how spin populations can be modulated via polarization and power, advancing spintronic device engineering.

Contribution

It introduces a method to manipulate the Rashba effect in Ge/SiGe quantum wells using optical excitation, enabling spin control in group-IV heterostructures.

Findings

Threefold increase in circular polarization with pump power

Observation of quantum-confined Stark effect-induced redshift

Effective modulation of spin populations via optical means

Abstract

The Rashba effect in Ge/Si$_{0.15}$Ge$_{0.85}$ multiple quantum wells embedded in a p-i-n diode is studied through polarization and time-resolved photoluminescence. In addition to a sizeable redshift arising from the quantum-confined Stark effect, a threefold enhancement of the circular polarization degree of the direct transition is obtained by increasing the pump power over a 2kW/cm$^2$ range. This marked variation reflects an efficient modulation of the spin population and is further supported by dedicated investigations of the indirect gap transition. This study demonstrates a viable strategy to engineer the spin-orbit Hamiltonian through contactless optical excitation and opens the way towards the electro-optical manipulation of spins in quantum devices based on group-IV heterostructures.