Berlin 2015 – scientific programme

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TT: Fachverband Tiefe Temperaturen

TT 102: Transport: Quantum Dots, Quantum Wires, Point Contacts 2 (jointly with HL)

TT 102.12: Talk

Thursday, March 19, 2015, 18:15–18:30, A 053

Charge fluctuation effects in superconductor-quantum dot hybrid systems — •Sebastian Pfaller, Andrea Donarini, and Milena Grifoni — Institut I - Theoretische Physik Universität Regensburg

In a recent experiment [1] quasi particle transport through a carbon nanotube quantum dot coupled to superconducting (SC) leads was investigated both experimentally and theoretically. While most of the features could be explained by a perturbative theory up to lowest order in quasi particles tunnelling, other features like the broadening of the differential conductance peaks were not captured.

In order to account for these effects, we include charge fluctuation processes of quasi particles by extending the dressed second order theory of Kern et al. [2] to the case of SC leads. This yields an intrinsic broadening of the quantum dots energy levels, and, consequently, a renormalization of the sharp peaks coming from the BCS density of states. Moreover, new transport channels are obtained. They appear as peaks at zero and finite bias in the dI/dV-stability diagrams.

[1] M. Gaass, S. Pfaller, T. Geiger et al., Phys. Rev. B 89, 241405 (2014).

[2] J. Kern, and M. Grifoni, Eur. Phys. J. B 86, 384 (2013).