Valley interference and spin exchange at the atomic scale in silicon

Abstract

Tunneling is a fundamental quantum process with no classical equivalent, which can compete with Coulomb interactions to give rise to complex phenomena. Phosphorus dopants in silicon can be placed with atomic precision to address the different regimes arising from this competition. However, they exploit wavefunctions relying on crystal band symmetries, which tunneling interactions are inherently sensitive to. Here we directly image lattice-aperiodic valley interference between coupled atoms in silicon using scanning tunneling microscopy. Our atomistic analysis unveils the role of envelope anisotropy, valley interference and dopant placement on the Heisenberg spin exchange interaction. We find that the exchange can become immune to valley interference by engineering in-plane dopant placement along specific crystallographic directions. A vacuum-like behaviour is recovered, where the exchange is maximised to the overlap between the donor orbitals, and pair-to-pair variations limited to a factor of less than 10 considering the accuracy in dopant positioning. This robustness remains over a large range of distances, from the strongly Coulomb interacting regime relevant for high-fidelity quantum computation to strongly coupled donor arrays of interest for quantum simulation in silicon.

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• Quasiparticle excitations in a one-dimensional interacting topological insulator: Application for dopant-based quantum simulation
• Engineering local strain for single-atom nuclear acoustic resonance in silicon
• Hole in one: Pathways to deterministic single-acceptor incorporation in Si(100)-2$\times$1
• Optimisation of electrically-driven multi-donor quantum dot qubits
• Hydrogenic Spin-Valley states of the Bromine donor in 2H-MoTe${}_2$
• Novel characterisation of dopant-based qubits
• Influence of sample momentum space features on scanning tunnelling microscope measurements
• Su-Schrieffer-Heeger-Hubbard model at quarter filling: effects of magnetic field and non-local interactions
• Towards Utilizing Scanning Gate Microscopy as a High-Resolution Probe of Valley Splitting in Si/SiGe Heterostructures
• Atomic scale visualization of the p-d hybridization in III-V semiconductors doped with transition metal impurities
• Silicon Donor Array as a Disordered One-Dimensional Electron Gas