Spin-filtered measurements of Andreev bound states in semiconductor-superconductor nanowire devices
D. van Driel (TU Delft - QuTech Advanced Research Centre, TU Delft - QRD/Kouwenhoven Lab, Kavli institute of nanoscience Delft)
Guanzhong Wang (TU Delft - QuTech Advanced Research Centre, TU Delft - QRD/Wimmer Group, Kavli institute of nanoscience Delft)
Alberto Bordin (Kavli institute of nanoscience Delft, TU Delft - QuTech Advanced Research Centre, TU Delft - QRD/Kouwenhoven Lab)
Nick van Loo (TU Delft - QRD/Kouwenhoven Lab, Kavli institute of nanoscience Delft, TU Delft - QuTech Advanced Research Centre)
F. Zatelli (TU Delft - QRD/Kouwenhoven Lab, TU Delft - QuTech Advanced Research Centre, Kavli institute of nanoscience Delft)
G.P. Mazur (TU Delft - QRD/Wimmer Group, Kavli institute of nanoscience Delft, TU Delft - QuTech Advanced Research Centre)
D. Xu (Kavli institute of nanoscience Delft, TU Delft - QuTech Advanced Research Centre, TU Delft - BUS/Quantum Delft)
Sasa Gazibegovic (Eindhoven University of Technology)
Ghada Badawy (Eindhoven University of Technology)
Erik P.A.M. Bakkers (Eindhoven University of Technology)
Leo P. Kouwenhoven (TU Delft - QN/Kouwenhoven Lab, TU Delft - QuTech Advanced Research Centre, Kavli institute of nanoscience Delft)
T. Dvir (TU Delft - QuTech Advanced Research Centre, Kavli institute of nanoscience Delft, TU Delft - QRD/Kouwenhoven Lab)
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Abstract
Semiconductor nanowires coupled to superconductors can host Andreev bound states with distinct spin and parity, including a spin-zero state with an even number of electrons and a spin-1/2 state with odd-parity. Considering the difference in spin of the even and odd states, spin-filtered measurements can reveal the underlying ground state. To directly measure the spin of single-electron excitations, we probe an Andreev bound state using a spin-polarized quantum dot that acts as a bipolar spin filter, in combination with a non-polarized tunnel junction in a three-terminal circuit. We observe a spin-polarized excitation spectrum of the Andreev bound state, which can be fully spin-polarized, despite strong spin-orbit interaction in the InSb nanowires. Decoupling the hybrid from the normal lead causes a current blockade, by trapping the Andreev bound state in an excited state. Spin-polarized spectroscopy of hybrid nanowire devices, as demonstrated here, is proposed as an experimental tool to support the observation of topological superconductivity.
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