Dresden 2014 – wissenschaftliches Programm

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TT: Fachverband Tiefe Temperaturen

TT 9: Transport: Quantum Dots, Quantum Wires, Point Contacts I (organized by TT)

TT 9.10: Vortrag

Montag, 31. März 2014, 12:00–12:15, BEY 81

The interplay of the proximity and Kondo effects in spin-resolved transport through quantum dots — •Krzysztof P. Wójcik and Ireneusz Weymann — Faculty of Physics, Adam Mickiewicz University, Umultowska 85, 61-614 Poznań, Poland

Transport properties of hybrid quantum dots coupled to ferromagnetic (FM) and superconducting (SC) leads are studied by means of the numerical renormalization group method [1,2]. By constructing the full density matrix of the system [3], the linear conductance and respective spectral functions are calculated. Aiming to emphasize the role of Andreev processes in transport, we model the quantum dot coupled to the superconductor by an effective Hamiltonian in the limit of large superconducting gap [4]. First, a three-terminal setup is considered, for which we study the proximity effect on the spin-dependent current flowing between the two FM leads. Then, the transport properties in a two-terminal setup, with one FM and one SC lead, are analyzed. In this case we focus on the interplay of the exchange field induced by FM lead, the Kondo effect and the Andreev processes. We show that the conductance generally depends on the ratio of these three quantities, leading to nontrivial transport behavior.

[1] K. G. Wilson, Rev. Mod. Phys. 47, 773 (1975).

[2] We use the open-access Budapest NRG code, O. Legeza, C. P. Moca, A. I. Toth, I. Weymann, G. Zarand, arXiv:0809.3143 (2008).

[3] A. Weichselbaum, J. von Delft, Phys. Rev. Lett. 99, 076402 (2007).

[4] Y. Tanaka, N. Kawakami, A. Oguri, J. Phys. Soc. Jap. 76, 074701 (2007).