Paramagnetic Breakdown of Superconductivity in Ultrasmall Metallic Grains

Abstract

We study the magnetic-field-induced breakdown of superconductivity in nm-scale metal grains having a mean electron level spacing $d\simeq \tilde{\Delta }$ (bulk gap). Using a generalized variational BCS approach that yields good qualitative agreement with measured spectra, we argue that Pauli paramagnetism dominates orbital diamagnetism, as in the case of thin films in a parallel magnetic field. However, the first-order transition observed for the latter can be made continuous by finite size effects. The mean-field procedure of describing the system by a single pairing parameter $\Delta$ breaks down for $d\simeq \tilde{\Delta }$.

4 pages of revtex, 3 postscript figures, uses psfrag.sty, epsfig.sty. Slightly revised and improved version, matching published version

References in corpus (1)

• Gate-Voltage Studies of Discrete Electronic States in Al Nanoparticles

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