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TT: Fachverband Tiefe Temperaturen

TT 6: Transport: Nanoelectronics I - Quantum Dots, Wires, Point Contacts 1

TT 6.1: Talk

Monday, March 26, 2012, 09:30–09:45, BH 334

Transport through multiple quantum dots coupled to superconducting leads — •Sebastian Pfaller and Milena Grifoni — Institut für Theoretische Physik, Universität Regensburg

We present a microscopic theory of transport through quantum dot set-ups coupled to superconducting leads. We derive a master equation for the reduced density matrix to lowest order in the tunneling Hamiltonian and focus on quasi-particle tunneling. In particular, we apply the theory to a quantum double dot with independently gated dots; considering the dots in series as well as in parallel configuration. Negative differential conductance, as well as the expected gap of the Coulomb diamonds proportional to the superconducting gap, are observed. Moreover, a current flows in the Coulomb blockade region due to thermally excited quasiparticles. These thermal excitations can be used to identify transitions through excited states in the ``honeycomb'' shaped stability diagrams.