Josephson junction π-0 transition induced by orbital hybridization in a double quantum dot

Rousan Debbarma, Athanasios Tsintzis, Markus Aspegren, Rubén Seoane Souto, Sebastian Lehmann, Kimberly Dick, Martin Leijnse, Claes Thelander

Published 2023-11-20Version 1

In this work, we manipulate the phase shift of a Josephson junction using a parallel double quantum dot (QD). By employing a superconducting quantum interference device, we determine how orbital hybridization and detuning affect the current-phase relation in the Coulomb blockade regime. For weak hybridization between the QDs, we find $\pi$ junction characteristics if at least one QD has an unpaired electron. Notably the critical current is higher when both QDs have an odd electron occupation. By increasing the inter-QD hybridization the critical current is reduced, until eventually a $\pi$-0 transition occurs. A similar transition appears when detuning the QD levels at finite hybridization. Based on a zero-bandwidth model, we argue that both cases of phase-shift transitions can be understood considering an increased weight of states with a double occupancy in the ground state and with the Cooper pair transport dominated by local Andreev reflection.