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SM ISO690:2012 GLADILIN, Vladimir, FOMIN, Vladimir, DEVREESE, Josef T.. Magnetic susceptibility of ultrasmall superconductor grains. In: Physical Review B - Condensed Matter and Materials Physics, 2004, vol. 70, pp. 144506-1-144506-15. ISSN 1098-0121. DOI: https://doi.org/10.1103/PhysRevB.70.144506 |
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Physical Review B - Condensed Matter and Materials Physics | ||||||
Volumul 70 / 2004 / ISSN 1098-0121 /ISSNe 1550-235X | ||||||
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DOI:https://doi.org/10.1103/PhysRevB.70.144506 | ||||||
Pag. 144506-1-144506-15 | ||||||
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For assemblies of superconductor nanograins, the magnetic response is analyzed as a function of both temperature and magnetic field. In order to describe the interaction energy of electron pairs for a huge number of many-particle states, involved in calculations, we develop a simple approximation, based on the Richardson solution for the reduced BCS Hamiltonian and applicable over a wide range of the grain sizes and interaction strengths at arbitrary distributions of single-electron energy levels in a grain. Our study is focused upon ultrasmall grains, where both the mean value of the nearest-neighbor spacing of single-electron energy levels in a grain and variations of this spacing from grain to grain significantly exceed the superconducting gap in bulk samples of the same material. For these ultrasmall superconductor grains, the overall profiles of the magnetic susceptibility as a function of magnetic field and temperature are demonstrated to be qualitatively different from those for normal grains. We show that the analyzed signatures of pairing correlations are sufficiently stable with respect to variations of the average value of the grain size and its dispersion over an assembly of nanograins. The presence of these signatures does not depend on a particular choice of statistics, obeyed by single-electron energy levels in grains. |
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Cuvinte-cheie article, chemical interaction, electron, energy, grain, Hamilton scale, magnetic field, magnetism, nanoparticle, reduction, statistical analysis, Superconductor, Temperature dependence |
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