VietNam 2013 

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


 Nanophysics: from fundamentals to applications

(the return)


Wednesday 7

› 15:50 - 16:10 (20min)
Waiting time distributions for the transport through a quantum dot coupled to normal and superconducting leads
Christina Pöltl  1, *@  , Leila Rajabi  1@  , Governale Michele  1, *@  
1 : Victoria University of Wellington  -  Website
School of Physical and Chemical Sciences, Victoria University of Wellington, P.O. Box 600, Wellington 6140, New Zealand -  New Zealand
* : Corresponding author

We study the waiting time distributions (WTDs) [1] of a single-level, interacting quantum dot coupled to one normal and one superconducting lead with the aim to obtain information on the short-time dynamics associated with the proximity effect in a nano-scale structure. Since we are interested in the coherent oscillations of Cooper pairs between the dot and the superconductor, we consider the limit of a large superconducting gap for which quasiparticle transport is suppressed. In this regime dot and superconductor can be described as combined system with an effective Hamiltonian [2]. The coupling between the proximised dot and the normal lead is then treated within a non-equilibrium perturbation approach.

We find that the elements of the WTD matrix exhibit an oscillatory behaviour, which is a direct consequence of the coherent exchange of Cooper pairs between the dot and the superconductor. The oscillations are most pronounced when the empty and the doubly-occupied state are in resonance and therefore the non-equilibrium proximity effect in the dot is maximum. These features of the system dynamics are not accessible via the zero-frequency full counting statistics but appear in the finite-frequency noise. Finally, we define a WTD conditional on the initial state. Such a quantity could be easier to measure for the localised states, since these are easy to prepare.

[1] T. Brandes, Ann. Phys. 17(7), 477 (2008).

[2] A.V. Rozhkov and D.P. Arovas, Phys. Rev. B 62, 6687 (2000).

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