Absence of the Rashba effect in undoped asymmetric quantum wells

TL;DR

This paper challenges the common belief that structural asymmetry in quantum wells induces a significant Rashba spin-orbit effect, showing experimentally and theoretically that undoped asymmetric wells lack this effect, impacting spintronic device design.

Contribution

The study provides evidence that inversion asymmetry alone does not produce a Rashba effect in undoped quantum wells, contradicting previous assumptions and clarifying fundamental physics.

Findings

No Rashba effect observed in undoped asymmetric quantum wells

Experimental and theoretical results show zero spin-orbit field in these structures

Implications for spintronic device design and fundamental physics understanding

Abstract

To an electron moving in free space an electric field appears as a magnetic field which interacts with and can reorient the electron spin. In semiconductor quantum wells this spin-orbit interaction seems to offer the possibility of gate-voltage control in spintronic devices but, as the electrons are subject to both ion-core and macroscopic structural potentials, this over-simple picture has lead to intense debate. For example, an externally applied field acting on the envelope of the electron wavefunction determined by the macroscopic potential, underestimates the experimentally observed spin-orbit field by many orders of magnitude while the Ehrenfest theorem suggests that it should actually be zero. Here we challenge, both experimentally and theoretically, the widely held belief that any inversion asymmetry of the macroscopic potential, not only electric field, will produce a significant spin-orbit field for electrons. This conclusion has far-reaching consequences for the design of spintronic devices while illuminating important fundamental physics.