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Even-odd effect in Andreev Transport through a Carbon Nanotube Quantum Dot

A. Eichler·M. Weiss·S. Oberholzer·C. Schonenberger·A. Levy Yeyati·J. C. Cuevas
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Abstract

We have measured the current(I)-voltage(V) characteristics of a single-wall carbon nanotube quantum dot coupled to superconducting source and drain contacts in the intermediate coupling regime. Whereas the enhanced differential conductance dI/dV due to the Kondo resonance is observed in the normal state, this feature around zero bias voltage is absent in the superconducting state. Nonetheless, a pronounced even-odd effect appears at finite bias in the $dI/dV$ sub-gap structure caused by Andreev reflection. The first-order Andreev peak appearing around V=Δ/e is markedly enhanced in gate-voltage regions, in which the charge state of the quantum dot is odd. This enhancement is explained by a `hidden' Kondo resonance, pinned to one contact only. A comparison with a single-impurity Anderson model, which is solved numerically in a slave-boson meanfield ansatz, yields good agreement with the experiment.

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A. Eichler, M. Weiss, S. Oberholzer, C. Schonenberger, A. Levy Yeyati, J. C. Cuevas. 2007-03-02. Even-odd effect in Andreev Transport through a Carbon Nanotube Quantum Dot. https://doi.org/10.1103/physrevlett.99.126602

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