Evidence of Andreev blockade in a double quantum dot coupled to a superconductor

Abstract

We design and investigate an experimental system capable of entering an electron transport blockade regime in which a spin-triplet localized in the path of current is forbidden from entering a spin-singlet superconductor. To stabilize the triplet a double quantum dot is created electrostatically near a superconducting lead in an InAs nanowire. The dots are filled stochastically with electrons of either spin. The superconducting lead is a molecular beam epitaxy grown Al shell. The shell is etched away over a wire segment to make room for the double dot and the normal metal gold lead. The quantum dot closest to the normal lead exhibits Coulomb diamonds, the dot closest to the superconducting lead exhibits Andreev bound states and an induced gap. The experimental observations compare favorably to a theoretical model of Andreev blockade, named so because the triplet double dot configuration suppresses Andreev reflections. Observed leakage currents can be accounted for by finite temperature. We observe the predicted quadruple level degeneracy points of high current and a periodic conductance pattern controlled by the occupation of the normal dot. Even-odd transport asymmetry is lifted with increased temperature and magnetic field. This blockade phenomenon can be used to study spin structure of superconductors. It may also find utility in quantum computing devices that utilize Andreev or Majorana states.

Written using The Block Method. Data on Zenodo DOI: 10.5281/zenodo.4446186

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Cited by in corpus (10)

• Josephson current via spin and orbital states of a tunable double quantum dot
• Spin-filtered measurements of Andreev bound states
• Subgap dynamics of double quantum dot coupled between superconducting and normal leads
• Microwave Signatures of Topological Superconductivity in Planar Josephson Junctions
• Fermionic quantum computation with Cooper pair splitters
• Ubiquitous missing first Shapiro step in Al-InSb nanosheet Josephson junctions
• Properties of multiterminal superconducting nanostructure with double quantum dot
• DC Josephson effect between two Yu-Shiba-Rusinov bound states
• Interplay between evanescent scattering modes and finite dispersion in superconducting junctions
• Transient triplet blockade in Andreev junction