Multiple Andreev reflections in a quantum dot coupled to superconductors: Effects of spin-orbit coupling
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We study the out-of-equilibrium current through a multilevel quantum dot contacted to two superconducting leads and in the presence of Rashba and Dresselhaus spin-orbit couplings, in the regime of strong dot-lead coupling. The multiple Andreev reflection (MAR) subgap peaks in the current voltage characteristics are found to be modified (but not suppressed) by the spin-orbit interaction, in a way that strongly depends on the shape of the dot confining potential. In a perfectly isotropic dot the MAR peaks are enhanced when the strength $α_R$ and $α_D$ of Rashba and Dresselhaus terms are equal. When the anisotropy of the dot confining potential increases the dependence of the subgap structure on the spin-orbit angle $θ=\arctan(α_D/α_R)$ decreases. Furthermore, when an in-plane magnetic field is applied to a strongly anisotropic dot, the peaks of the non-linear conductance oscillate as a function of the magnetic field angle, and the location of the maxima and minima allows for a straightforward read-out of the spin-orbit angle $θ$.
Final version published in Phys. Rev. B. (typos corrected; more details specified in the text and in the abstract; color scale of Fig.9 improved)
Final version published in Phys. Rev. B. (typos corrected; more details specified in the text and in the abstract; color scale of Fig.9 improved)