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Article Dans Une Revue Journal of Physics: Condensed Matter Année : 2012

Quantum cascades in nano-engineered superconductors: geometrical, thermal and paramagnetic effects

Yajiang Chen
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A. A. Shanenko
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F. M. Peeters
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Résumé

The effect of a parallel magnetic field on the orbital motion of electrons in high-quality superconducting nanowires resulting in a superconductor-to-normal transition which occurs through a cascade of jumps in the order parameter as a function of the magnetic field. Such cascades originate from the transverse size quantization that splits the conduction band into a series of subbands. Here, based on a numerical solution of the Bogoliubov-de Gennes equations for a hollow nanocylinder, we investigate how the quantum-size cascades depend on the confining geometry, i.e., by changing the cylinder radius R and its thickness d we cover the range from the nanowire-like to the nanofilm-like regime. The cascades are shown to become much less pronounced when increasing R=d, i.e., when the nanofilm-like regime is approached. When the temperature is non-zero they are thermally smoothed. This includes the spin-magnetic-field interaction which reduces the critical (depairing) parallel magnetic field Hc;k but does not have any qualitative effect on the quantum cascades. From our calculations it is seen that the paramagnetic limiting field Hpar significantly exceeds Hc;k even in extremely narrow nanocylinders, i.e., when R; d are down to a few nanometers, and Hc;k is only about 10% larger when switching-off the spin-magnetic-field interaction in this case. Both characteristic fields, Hc;k and Hpar, exhibit pronounced quantum-size oscillations. We demonstrate that the quantum cascades and the quantum-size oscillations survive in the presence of surface roughness.
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hal-00731851 , version 1 (28-08-2018)

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Paternité - Pas d'utilisation commerciale - Partage selon les Conditions Initiales

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Yajiang Chen, A. A. Shanenko, Mihail D. Croitoru, F. M. Peeters. Quantum cascades in nano-engineered superconductors: geometrical, thermal and paramagnetic effects. Journal of Physics: Condensed Matter, 2012, 24 (26), pp.265702. ⟨10.1088/0953-8984/24/26/265702⟩. ⟨hal-00731851⟩

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