Multiscale theory of valley splitting

TL;DR

This paper develops a multiscale analytical theory combining effective mass and tight binding methods to understand valley coupling in silicon quantum wells, relevant for quantum computing devices.

Contribution

It introduces a novel multiscale analytical framework that bridges atomistic and continuum models for valley coupling in semiconductor quantum wells.

Findings

Provides a fully analytical approach to valley splitting.

Offers insights applicable to silicon qubits and GaAs wells.

Enhances understanding of interface effects on valley coupling.

Abstract

The coupling between $z$ valleys in the conduction band of a Si quantum well arises from phenomena occurring within several atoms from the interface, thus ruling out a theoretical description based on pure effective mass theory. However, the complexity and size of a realistic device precludes an analytical atomistic description. Here, we develop a fully analytical multiscale theory of valley coupling, by combining effective mass and tight binding approaches. The results are of particular interest for silicon qubits and quantum devices, but also provide insight for GaAs quantum wells.