Spin relaxation of a donor electron coupled to interface states

Peihao Huang, Garnett W. Bryant

Published 2017-10-20Version 1

An electron spin qubit in a silicon donor atom is a promising candidate for quantum information processing because of its long coherence time. To be sensed with a single-electron transistor, the donor atom is usually located near an interface, where the donor states can be coupled with interface states. Here we study the spin relaxation mechanisms arising from the coupling of a donor to confined interface states. We find that both Zeeman interaction and spin-orbit interaction can hybridize spin and orbital states, each contributing to phonon-assisted spin relaxation in addition to the spin relaxation for a bulk donor or a quantum dot. When the applied magnetic field $B$ is weak (compare to orbital spacing), the spin relaxation due to Zeeman interaction and spin-orbit interaction show the same $B^5$ dependence on the magnitude of $B$ field, but show different angular dependencies on the orientation of $B$ field. We find that there are peaks (hot-spots) in the $B$-dependent and detuning dependent spin relaxation due to strong hybridization of orbital states with opposite spin. We also find spin relaxation dips (cool-spots) due to the interference of different relaxation paths. The electrically tunable spin relaxation hot-spots and cool-spots can be useful for fast spin initialization and the preservation of quantum information during the transfer of spin qubit.