Modeling dopants in silicon: application to atomic-scale Si qubit systems.

Dopants in silicon are strong candidates for qubits in scalable, atom-based, solid-state quantum systems due to their long decoherence times and Si nanofabrication infrastructure. In these devices, an impurity atom binds a donor electron at low temperatures and information is stored either in the electron or the dopant nuclear spin. Typically, tight-binding (TB) theory is expected to provide a good computational model with reasonable precision. However, calculations based on simple central cell potential cutoff failed to predict the well-established energy degeneracies for a variety of bulk Si tight-binding models, hinting missing corrections in the model. We present TB calculations using several new corrections including the induced nearest neighbor hopping, the varying screened potential, and the orthogonalization of the on-site wavefunctions. We also discuss the consequences of applying these atomic scale corrections on the dopant models, including effects on the hyperfine interactions and STM imaging of dopants. Finally, we discuss how these models can be potential guides for experiments in many-body physics using atom-based devices.