Valley interference and spin exchange at the atomic scale in silicon
arXiv:2105.10931 · doi:10.1038/s41467-020-19835-1
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.
References in corpus (9)
- Surface codes: Towards practical large-scale quantum computation
- Layer-dependent properties of SnS2 and SnSe2 novel two-dimensional materials
- Valley susceptibility of an interacting two-dimensional electron system
- Coupling of three-spin qubits to their electric environment
- Imaging quasi-particle wavefunctions in quantum dots via tunneling spectroscopy
- A precise CNOT gate in the presence of large fabrication induced variations of the exchange interaction strength
- Donor hyperfine Stark shift and the role of central-cell corrections in tight-binding theory
- Spatially resolved resonant tunneling on single atoms in silicon
- Statistical exchange-coupling errors and the practicality of scalable silicon donor qubits