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Register a new userParity-dependent shot noise and spin-flip relaxation process in a hybrid superconductor-nanowire quantum dot
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We report shot noise measurements for a quantum dot formed in an InAs nanowire suspended between superconducting electrodes. We find a clear alternation for the shot noise value in the Coulomb blockade regime between even and odd electron occupation in the dot, indicating that super-Poissonian (Poissonian) shot noise with the Fano factor reaching around 2 (1) occurs for even (odd) parity. With increasing magnetic field, the parity effect disappears and all the regimes show the Fano factor of around 1. The whole observation in our experiments quantitatively agrees with simulation obtained from full-counting statistics of cotunneling including spin-flip relaxation process, which corresponds to modelling electron motion in a quantum dot with strong spin-orbit interaction.
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We study the impacts of the magnetic field direction on the spin-manipulation and the spin-relaxation in a one-dimensional quantum dot with strong spin-orbit coupling. The energy spectrum and the corresponding eigenfunctions in the quantum dot are obtained exactly. We find that no matter how large the spin-orbit coupling is, the electric-dipole spin transition rate as a function of the magnetic field direction always has a $pi$ periodicity. However, the phonon-induced spin relaxation rate as a function of the magnetic field direction has a $pi$ periodicity only in the weak spin-orbit coupling regime, and the periodicity is prolonged to $2pi$ in the strong spin-orbit coupling regime.
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