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O: Fachverband Oberflächenphysik

O 4: Transport: Quantum Dots, Wires, Point Contacts 1 (jointly with HL and TT)

O 4.11: Vortrag

Montag, 11. März 2013, 12:15–12:30, H20

Thermoelectric efficiency of a driven double quantum dot — •Federica Haupt¹, Stefan Juergens¹, Michael Moskalets², and Janine Splettstoesser¹ — ¹RWTH Aachen University, Aachen, Germany — ²Kharkiv Polytechnical Institute, Kharkiv, Ukraine

By applying phase-shifted AC signals to the gates of two quantum dots connected in series, it is possible to transfer charge from one lead to another in a quantized way [1,2], even in the presence of an applied bias voltage or a temperature gradient. In this work we investigate the thermoelectric properties of such a double quantum dot device. We show that not only charge but also heat can be pumped in a quantized way. If the modulation frequency Ω is sufficiently small, we find regimes in which the unit of heat 2 π k_BT ln2 is transported during each period, where T is the temperature of the considered lead and the factor ln2 stems from spin degeneracy. This would open 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 real device is limited by dissipative effects due to leakage currents and finite time operation, which we rigorously take into account by means of a real-time diagrammatic approach in the regime of weak coupling to the leads. We show that despite these dissipative effects, efficiencies up to 70% of the maximal theoretical value can be reached.
[1] H. Pothier, et al., Europhys. Lett 17, 249 (1992)
S. J. Chorley, et al. App. Phys. Lett. 100, 143104 (2012).