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TT: Fachverband Tiefe Temperaturen
TT 54: SC: Heterostructures, Andreev Scattering, Proximity Effect
TT 54.5: Talk
Thursday, March 17, 2011, 16:30–16:45, HSZ 301
Adiabatic Cooper pair pumping through quantum dots — •Bastian Hiltscher1, Michele Governale2, Janine Splettstoesser3, and Jürgen König1 — 1Theoretische Physik, Universität Duisburg-Essen and CeNIDE — 2School of Chemical and Physical Sciences, Victoria University of Wellington — 3Institut für Theoretische Physik A, RWTH Aachen University
Motivated by recent experimental work [1] we investigate splitting of Cooper pairs in adiabatic pumping. We consider (i) a quantum dot with Zeeman split levels tunnel coupled to a normal and a superconductor and (ii) two quantum dots tunnel coupled to the same superconductor and each dot coupled to a normal conductor.
We combine the means of two different theories. On the one hand a systematic perturbation expansion in tunnel-coupling strength between quantum dots and superconductors [2] and on the other hand an adiabatic expansion using that the pumping period is small compared to the lifetime of a certain state [3].
We find that the pumped charge and the linear conductance show the same dependence on the average dot level position. The underlying tunneling processes are discussed. In order to figure out processes where a Cooper pair is split we compare the properties of Cooper pair pumping with single-electron pumping. The dependence on the average dot-level position turns out to be the main distinguishing feature.
Hofstetter et al., Nature 461, 960 (2009); Herrmann et al., PRL 104, 026801 (2010).
Governale et al., PRB 77, 134513 (2008).
Splettstoesser et al., PRB 74, 085305 (2006).