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

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.

Lower bound on the spread of valley splitting in Si/SiGe quantum wells induced by atomic rearrangement at the interface

“…[31][32][33][34] Consequently, this poses a significant challenge to the scalability of silicon qubits within the context of universal faulttolerant quantum computing. [34] Both extensive theoretical work [32,[35][36][37][38][39][40][41][42][43][44][45][46][47][48][49] and experimental observations [24,27,28,34,[50][51][52][53][54][55] have pointed out that the E VS depends sensitively on the microscopic details near the interface. Particularly, a recent investigation [34] delves into the atomic-scale reconstruction of the Si/SiGe interface and reveals its three-dimensional (3D) morphology, highlighting the microscopic alloying concentration fluctuation along the confinement direction (i.e., z axis in Fig.…”