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

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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Cited by in corpus (5)

• Josephson junction π-0 transition induced by orbital hybridization in a double quantum dot
• Magnon-mediated topological superconductivity in a quantum wire
• Tunable Fano and Dicke effects in quantum transport of double quantum dots sandwiched between topological insulators
• DC Josephson effect between two Yu-Shiba-Rusinov bound states
• Spin-photon coupling using circular double quantum dots