Regensburg 2022 – wissenschaftliches Programm

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TT: Fachverband Tiefe Temperaturen

TT 26: Superconductivity: Tunnelling and Josephson Junctions

TT 26.4: Vortrag

Donnerstag, 8. September 2022, 10:15–10:30, H10

A particle conserving approach to AC-DC driven interacting quantum dots with superconducting leads — •Julian Siegl, Jordi Picó-Cortés, and Milena Grifoni — Universität Regensburg, Regensburg, Germany

The combined action of a DC bias and a microwave drive on the transport characteristic of a superconductor-quantum dot-superconductor junction is investigated. To cope with non-equilibrium effects and interactions in the quantum dot, we develop a general formalism for the dynamics of the density operator based on a particle conserving approach to superconductivity. An exact generalized master equation for the reduced dot operator is obtained that treats the interaction inside the dot exactly and showcases the characteristic bichromatic response due to the combination of the AC Josephson effect and an AC voltage. In the weak coupling limit, analytical expressions for the stationary current and the reduced dot operator are provided. In this regime, beside quasiparticle transport, we show that superconducting correlations manifest in anomalous pair tunneling processes involving the tunneling of a Cooper pair. Photon assisted processes allow for subgap transport and rich current-voltage characteristics. For example, we find total current inversion, in which the current flows against the applied DC bias for suitable parameter regimes.