Regensburg 2013 – wissenschaftliches Programm

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TT: Fachverband Tiefe Temperaturen

TT 8: Transport: Quantum Dots, Wires, Point Contacts 1 (jointly with HL and O)

TT 8.5: Vortrag

Montag, 11. März 2013, 10:30–10:45, H20

Magnon-driven quantum-dot heat engine — •Björn Sothmann and Markus Büttiker — Département de Physique Théorique, Université de Genève, CH-1211 Genève 4, Switzerland

Recently, thermoelectric effects have generated a lot of interest. In Ref. [1], transport through two capacitively coupled quantum dots in a three-terminal setup was investigated in the Coulomb-blockade regime. It was shown how such a device can convert a heat current into a directed charge current. This converter is optimal in the sense that it transfers one electron for every quantum of energy delivered by the hot dot and thus allows to reach Carnot efficiency. A generalization to systems with many transport channels was analyzed in Ref. [2].

Here, we discuss a new class of devices where a single-level quantum dot is coupled to two ferromagnetic electrodes as well as to a ferromagnetic insulator at different temperatures [3]. We demonstrate that the system can convert a magnon current into a pure electron spin current or a spin-polarized electron current depending on the magnetic configuration. We analyze the maximal output power as well as the efficiency and show that the tight-coupling limit where heat and charge currents are proportional to each other can be reached.
[1] R. Sánchez and M. Büttiker, Phys. Rev. B 83, 085428 (2011).
B. Sothmann, R. Sánchez, A. N. Jordan and M. Büttiker, Phys. Rev. B 85, 205301 (2012).
B. Sothmann and M. Büttiker, EPL 99, 27001 (2012).