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arXiv · 2212.06484

Josephson current via spin and orbital states of a tunable double quantum dot

Rousan Debbarma·Markus Aspegren·Florinda Viñas Boström·Sebastian Lehmann·Kimberly Dick·Claes Thelander
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Abstract

Supercurrent transport is experimentally studied in a Josephson junction hosting a double quantum dot (DQD) with tunable symmetries. The QDs are parallel-coupled to two superconducting contacts and can be tuned between strong inter-dot hybridization and a ring geometry where hybridization is suppressed. In both cases, we observe supercurrents when the two interacting orbitals are either empty or filled with spins, or a combination. However, when each QD hosts an unpaired spin, the supercurrent depends on the spin ground state. It is strongly suppressed for the ring geometry with a spin-triplet ground state at zero external magnetic field. By increasing the QD hybridization, we find that a supercurrent appears when the ground state changes to spin-singlet. In general, supercurrents are suppressed in cases of spin doublet ground state, but an exception occurs at orbital degeneracy when the system hosts one additional spin, as opposed to three, pointing to a broken particle-hole symmetry.

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Rousan Debbarma, Markus Aspegren, Florinda Viñas Boström, Sebastian Lehmann, Kimberly Dick, Claes Thelander. 2022-12-13. Josephson current via spin and orbital states of a tunable double quantum dot. https://doi.org/10.1103/physrevb.106.l180507

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