Nature Communications: Spin-valley lifetimes in a silicon quantum dot with tunable valley splitting

June 27th, 2013  |  Published in All, News, Papers

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 siliconquantum 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.

Source: Nature Communications

Download the paper here. And be sure to download the Supplementary Material (ncomms3069) as well, which includes the new theory for spin-valley relaxation in realistic silicon quantum dots.

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