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TT: Fachverband Tiefe Temperaturen

TT 101: Transport - Poster Session

TT 101.2: Poster

Donnerstag, 3. April 2014, 15:00–19:00, P2

Nonequilibrium BCS-Anderson model- ISPI approach — •Stephan Weiss and Jürgen König — Theoretische Physik, Universität Duisburg-Essen and CENIDE, 47048 Duisburg, Germany

Using the scheme of iterative summation of real-time path integrals (ISPI) [1-2], we compute the I(V) characteristics of a single spin-degenerate quantum dot tunnel coupled to superconducting (BCS) leads. By means of a Hubbard-Stratonovich transformation, the path integral is mapped to a finite spin sum inheriting nonlocal-in-time correlations among the spins. Anomalous Green’s functions components are truncated according to the established rules [1-2] on the same footing as the normal Keldysh components. The remaining spin-path summation is capable for the ISPI scheme. Since we treat tunneling exactly to all orders, we are able to resolve the subgap structure in terms of multiple Andreev reflections (MAR). We present results of the I(V) for the non-perturbative regime (U/Γ, T/Γ, eV/Γ ≫ 1), whereas in the noninteracting limit we compare our results to previous analytical results [3]. For U/Γ≪ 1 we compare to a perturbative calculation [4] as well as to a real-time diagrammatic approach for Γ_S≪ 1 [5].
[1] S. Weiss, et al., Phys. Rev B, 77, 195316, (2008).
[2] S. Weiss, et al., Phys. Status Solidi B 250, 2298 (2013).
[3] A. Levy-Yeyati, et al., Phys. Rev. B 55, 6137(R) (1996).
[4] L. Dell Anna, et al., Phys. Rev. B 77, 104525 (2008).
[5] M. Governale, et al., Phys. Rev. B 77, 134513 (2008).