VietNam 2013 

IXth Rencontres du Vietnam
Quy-Nhon, August 4-10, 2013


 Nanophysics: from fundamentals to applications

(the return)


Monday 5
Dots and wires
Y. Gefen
› 15:00 - 15:30 (30min)
Thermoelectric performance of a quantum dot pump
Janine Splettstoesser  1@  
1 : RWTH Aachen University
Institut fuer Theorie der Statistischen Physik, RWTH Aachen University, Physikzentrum, D-52074 Aachen -  Germany

Nanoscale systems driven by time-dependent signals, such as quantum pumps, have recently attracted a lot of attention since they can serve as controlled sources of single particles.
I will address the thermoelectric performance of a double-dot device driven by time-dependently modulated gate voltages. If the modulation frequency $\Omega$ is sufficiently small, not only quantized charge pumping can be realized, but also the heat current flowing in the leads is shown to exhibit plateaux, proportional to the driving frequency, temperature and a factor ln2. The latter stems from spin degeneracy of the double-dot states involved into transport.
This opens the possibility of using the pumping cycle to transfer heat against a temperature gradient or to extract work from a hot reservoir with Carnot efficiency. However, the performance of a realistic device is limited by dissipative effects due to leakage currents and finite-frequency operation, which we take into account rigorously by means of a real-time diagrammatic approach in the weak-coupling regime. We show that despite these effects, the efficiency of a double-dot charge pump performing work against a dc-source can reach up to 70\% of the ideal value.S. Juergens, F. Haupt, M. Moskalets, and J. Splettstoesser, arXiv:1303.5225.

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