New Model Challenges Silicon Theories with Exact Valley Splitting
Researchers are developing a more accurate theoretical framework to understand valley splitting, a crucial parameter in silicon-based quantum devices, within strained Si/SiGe nanostructures. Lasse Ermoneit, Abel Thayil, and Thomas Koprucki, all from the Weierstrass Institute for Applied Analysis and Stochastics (WIAS), alongside Markus Kantner and colleagues, present a novel multi-valley envelope function theory that moves beyond limitations of conventional models. Their work addresses the challenges posed by atomically sharp interfaces and engineered Ge concentration profiles in modern heterostructures, where traditional approximations break down. By formulating an exact model incorporating Burt-Foreman theory and a valley-sector decomposition, the team demonstrates that conventional envelope function theory can produce unphysical, energy-reference dependent results. This research is significant because it not only identifies a fundamental flaw in existing models but also proposes a spectrally filtered local approximation that restores accuracy and energy-reference invariance, paving the way for more reliable design and optimisation of silicon-based quantum technologies. Controlling electrons in silicon and germanium nanostructures promises advances in high-speed computing and quantum technology. Accurate modelling of these materials has relied on approximations that are now being stretched to their limits by increasingly refined device designs. A new theoretical treatment offers a more precise way to predict electron behaviour in these complex structures. Scientists have developed a more accurate theoretical model for predicting valley splitting in silicon-germanium quantum wells, a critical parameter for building silicon-based spin qubits. These qubits, promising candidates for scalable quantum computers, rely on the precise control of electron behaviour within these nanostructures. Existing models struggle with the increasingly complex designs of modern heterost
