Extended interface states enhance valley splitting in Si/SiO2

TL;DR

This paper demonstrates that intrinsic interface states at Si/SiO2 interfaces can hybridize with valley states, significantly increasing valley splitting, especially in disordered interfaces, which aligns with recent experimental findings.

Contribution

It reveals a novel hybridization mechanism between interface states and valley states that enhances valley splitting in silicon quantum devices.

Findings

Hybridization with interface states increases valley splitting.

Disordered chemical bonds further enhance valley splitting.

Results agree with recent experimental observations.

Abstract

Interface disorder and its effect on the valley degeneracy of the conduction band edge remains among the greatest theoretical challenges for understanding the operation of spin qubits in silicon. Here, we investigate a counterintuitive effect occurring at Si/SiO2 interfaces. By applying tight binding methods, we show that intrinsic interface states can hybridize with conventional valley states, leading to a large ground state energy gap. The effects of hybridization have not previously been explored in details for valley splitting. We find that valley splitting is enhanced in the presence of disordered chemical bonds, in agreement with recent experiments.