Freiburg 2019 – wissenschaftliches Programm
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FM: Fall Meeting
FM 63: Poster: Enabling Technologies: Quantum Materials, Quantum Dots, Quantum Wires, Point Contacts and Superconducting Systems
FM 63.2: Poster
Mittwoch, 25. September 2019, 16:30–18:30, Tents
Phase transitions in double quantum dots coupled to superconducting leads — •Georgios Loukeris1, Martin Žonda1, Vladislav Pokorný2, Tomáš Novotný2, and Michael Thoss1 — 1Albert Ludwig University of Freiburg, Institute of Physics, Freiburg, Germany — 2Faculty of Mathematics and Physics, Charles University, Prague, Czech Republic
Various geometries of double quantum dots coupled to superconducting leads have been recently explored both theoretically and experimentally. It was shown that they can be used for the production of entangled electrons usable in computational protocols in solid state systems as well as for exploring complex quantum phase transitions. The advantage of double quantum dots is their tunability as individual gates can be used to control each dot separately. This can be utilized for setting the devices in different regimes. For example, if the dots are decoupled from each other, the gates can be used to set one dot to the so called 0-phase where its ground state is a BCS singlet and the other in π-phase with doublet ground state.
We investigate theoretically this situations by addressing a superconducting Anderson impurity model. We focus on how the properties of the junction change when we switch on the direct coupling between the dots. We show that the setup can be tuned to go trough various quantum phase transitions and crossovers. In addition the dependence of the supercurrent on the Josephson phase difference can have a complicated non-sinusoidal form.