Magnetic field dependence of valley splitting in realistic Si/SiGe quantum wells

TL;DR

This study explores how magnetic fields influence valley splitting in Si/SiGe quantum wells, revealing that atomic steps and wave function confinement cause interference effects and suppression of valley splitting, aligning with experimental observations.

Contribution

The paper provides a detailed numerical analysis of how atomic steps and magnetic fields affect valley splitting, offering quantitative insights into experimental suppression phenomena.

Findings

Atomic steps cause interference effects reducing valley splitting.

Magnetic field dependence results from lateral confinement of electrons.

Numerical simulations match experimental suppression of valley splitting.

Abstract

The authors investigate the magnetic field dependence of the energy splitting between low-lying valley states for electrons in a Si/SiGe quantum well tilted with respect to the crystallographic axis. The presence of atomic steps at the quantum well interface may explain the unexpected, strong suppression of the valley splitting observed in recent experiments. The authors find that the suppression is caused by an interference effect associated with multiple steps, and that the magnetic field dependence arises from the lateral confinement of the electronic wave function. Using numerical simulations, the authors clarify the role of step disorder, obtaining quantitative agreement with the experiments.