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Andreev bound states from quantum dots in proximitized Rashba nanowires

Olesia Dmytruk


LPS, bât 510, salle 208a, aîle sud

First, I will discuss the renormalization of the g-factor in semiconducting Rashba nanowires, consisting of a normal and superconducting section, at low magnetic fields [1]. If the potential barrier between the sections is high, a quantum dot is formed in the normal section. For harmonic (hard-wall) confinement, the effective g-factor of all quantum dot levels is suppressed exponentially (power law) in the product of the spin-orbit interaction wave vector and the quantum dot length. If the barrier between the two sections is removed, the g-factor of the emerging Andreev bound states saturates to a universal constant. Remarkably, the effective g-factor shows a pronounced peak at the spin-orbit energy as function of the chemical potentials. This provides a powerful tool to determine experimentally whether the spin-orbit interaction in the whole nanowire is uniform and, moreover, gives direct access to the spin-orbit interaction strengths of the nanowire via g-factor measurements.

Next, I will discuss a similar setup at large magnetic fields [2]. Even if there is no topological superconducting phase possible, there is a trivial Andreev bound state that becomes pinned exponentially close to zero energy as a function of magnetic field strength when the length of the quantum dot is tuned with respect to its spin-orbit length such that a resonance condition of Fabry-Perot type is satisfied. In this case, the Andreev bound state remains pinned near zero energy for Zeeman energies that exceed the characteristic spacing between Andreev bound state levels but that are smaller than the spin-orbit energy of the quantum dot. To support the analytical model, a numerical simulation of a hybrid system while explicitly incorporating a thin superconducting layer was performed, showing that all qualitative features of the analytical model are also present in the numerical results.

[1] O. Dmytruk, D. Chevallier, D. Loss, and J. Klinovaja, Phys. Rev. B 98, 165403 (2018).
[2] C. Reeg, O. Dmytruk, D. Chevallier, D. Loss, and J. Klinovaja, arXiv:1810.09840.

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