Paramagnetic Breakdown of Superconductivity in Ultrasmall Metallic Grains

Fabian Braun; Jan von Delft; D. C. Ralph; M. Tinkham

doi:10.1103/PhysRevLett.79.921

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Paramagnetic Breakdown of Superconductivity in Ultrasmall Metallic Grains

Fabian Braun, Jan von Delft, D. C. Ralph, M. Tinkham

DOI 10.1103/PhysRevLett.79.921 · Physical Review Letters

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Abstract

We study the magnetic-field-induced breakdown of superconductivity in nm-scale metal grains having a mean electron level spacing d≃Δ̃ (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 Δ breaks down for d≃Δ̃.

Source-reported materials — not catalogue approval

Formula	Reported Tc (K)	Pressure (GPa)	Type
Al Archive — visibility unverified Source-occurrence policy only; no material identity or catalogue acceptance is inferred from the formula.	—	Pressure not reported	unknown