Effect of quantum Hall edge strips on valley splitting in silicon quantum wells

TL;DR

This study investigates how quantum Hall edge strips influence valley splitting in silicon quantum wells, revealing a linear increase with magnetic field and independence from Hall density, aligning with theoretical models.

Contribution

It provides experimental evidence that valley splitting depends on edge strip density changes rather than bulk density, supporting a specific transport model.

Findings

Valley splitting increases linearly with magnetic field B.

Valley splitting is independent of Hall density.

Estimated valley splitting rate is 116 μeV per 10^11 cm^-2.

Abstract

We determine the energy splitting of the conduction-band valleys in two-dimensional electrons confined to low-disorder Si quantum wells. We probe the valley splitting dependence on both perpendicular magnetic field $B$ and Hall density by performing activation energy measurements in the quantum Hall regime over a large range of filling factors. The mobility gap of the valley-split levels increases linearly with $B$ and is strikingly independent of Hall density. The data are consistent with a transport model in which valley splitting depends on the incremental changes in density $eB/h$ across quantum Hall edge strips, rather than the bulk density. Based on these results, we estimate that the valley splitting increases with density at a rate of 116 $\mu$eV/10$^{11}$cm$^{-2}$, consistent with theoretical predictions for near-perfect quantum well top interfaces.