Interface and electromagnetic effects in the valley splitting of Si quantum dots

TL;DR

This paper presents a new 3D theoretical model to analyze how electromagnetic fields and interface quality affect valley splitting in silicon quantum dots, crucial for qubit performance.

Contribution

It introduces a comprehensive 3D model considering interface fluctuations and lateral confinement, highlighting electric field control and interface softness for valley splitting optimization.

Findings

Electric field significantly influences valley splitting.

Interface softness impacts the optimal heterostructure design.

Wider interfaces are preferable above a critical softness threshold.

Abstract

The performance and scalability of silicon spin qubits depend directly on the value of the conduction band valley splitting. In this work, we investigate the influence of electromagnetic fields and the interface width on the valley splitting of a quantum dot in a Si/SiGe heterostructure. We propose a new three-dimensional theoretical model within the effective mass theory for the calculation of the valley splitting in such heterostructures that takes into account the concentration fluctuation at the interfaces and the lateral confinement. With this model, we predict that the electric field is an important parameter for valley splitting engineering, since it can shift the probability distribution away from small valley splittings for some interface widths. We also obtain a critical softness of the interfaces in the heterostructure, above which the best option for spin qubits is to consider an interface as wide as possible.