Spectroscopy of Valley Splitting in a Silicon/Silicon-Germanium Two-Dimensional Electron Gas

TL;DR

This paper uses microwave spectroscopy to precisely measure valley splitting in a strained silicon quantum well, revealing a linear magnetic field dependence and temperature effects relevant for spin quantum computing.

Contribution

It provides the first accurate low-field valley splitting measurements using EVR and compares results with conventional methods, confirming theoretical predictions.

Findings

Linear magnetic field dependence of valley splitting

Strong low-field suppression consistent with theory

Resonance linewidth increases above 300 mK

Abstract

The lifting of the two-fold degeneracy of the conduction valleys in a strained silicon quantum well is critical for spin quantum computing. Here, we obtain an accurate measurement of the splitting of the valley states in the low-field region of interest, using the microwave spectroscopy technique of electron valley resonance (EVR). We compare our results with conventional methods, observing a linear magnetic field dependence of the valley splitting, and a strong low-field suppression, consistent with recent theory. The resonance linewidth shows a marked enhancement above $T\simeq 300$ mK.