Freiburg 2019 – scientific programme

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FM: Fall Meeting

FM 38: Enabling Technologies: Quantum Dots, Quantum Wires, Point Contacts and Excitonic Systems

FM 38.8: Talk

Tuesday, September 24, 2019, 15:45–16:00, 3043

Dephasing of Andreev bound states revealed by iterative summation of path integrals — •Stephan Weiss and Jürgen König — Theoretische Physik, Universität Duisburg-Essen, Lotharstr. 1, 47048 Duisburg & CENIDE

Multiple coherent reflections of electrons at superconductor/normal conductor interfaces lead to Andreev bound states (ABS), which have an energy that is smaller than the superconducting gap. As Andreev bound states are current-carrying, they may be probed within quantum-transport measurements. Coupling to a normal metal induces dephasing. We investigate a minimal model, which exhibit a tuneable ABS spectrum, i.e. an interacting quantum dot with a single spin-degenerate level that is brought into proximity to a superconductor. Iterative path-integral summations [1-3] are carried out to obtain the tunnelling current. Our method is numerically exact and treats spin-dependent resonant-tunnelling processes in a natural manner [2,3]. It furthermore allows to take into account small to intermediate Coulomb interactions. A tunnel-coupled normal metal is used to monitor the spectrum of the quantum dot together with the induced dephasing of the Andreev bound states over a wide range of gate- and bias voltages at finite temperatures [3].

[1] S. Weiss, et. al, Phys. Stat. Sol. B, 250, 2298 (2013).

[2] S. Weiss and J. König, submitted, (2019).

[3] S. Mundinar, Ph. Stegmann, J. König, and S. Weiss, Phys. Rev. B 99, 195457 (2019).