Abstract
Although silicon is a promising material for quantum computation, the degeneracy of the conduction band minima (valleys) must be lifted with a splitting sufficient to ensure the formation of well-defined and long-lived spin qubits. Here we demonstrate that valley separation can be accurately tuned via electrostatic gate control in a metal-oxide-semiconductor quantum dot, providing splittings spanning 0.3-0.8 meV. The splitting varies linearly with applied electric field, with a ratio in agreement with atomistic tight-binding predictions. We demonstrate single-shot spin read-out and measure the spin relaxation for different valley configurations and dot occupancies, finding one-electron lifetimes exceeding 2 s. Spin relaxation occurs via phonon emission due to spin-orbit coupling between the valley states, a process not previously anticipated for silicon quantum dots. An analytical theory describes the magnetic field dependence of the relaxation rate, including the presence of a dramatic rate enhancement (or hot-spot) when Zeeman and valley splittings coincide.
Keywords
ELECTRON-SPIN
Citation
DOI: 10.1038/ncomms3069
Date of this Version
6-2013
Recommended Citation
Yang, C. H.; Rossi, A.; Ruskov, R.; Lai, N. S.; Mohiyaddin, F. A.; Lee, S.; Tahan, C.; Klimeck, Gerhard; Morello, A.; and Dzurak, A. S., "Spin-valley lifetimes in a silicon quantum dot with tunable valley splitting" (2013). Birck and NCN Publications. Paper 1417.
https://docs.lib.purdue.edu/nanopub/1417