Pair transfer spectral function at finite temperature in nanometer-scale superconducting grains

R. Rossignoli; N. Canosa; J. L. Egido

doi:10.1103/PhysRevB.64.224511

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Pair transfer spectral function at finite temperature in nanometer-scale superconducting grains

R. Rossignoli, N. Canosa, J. L. Egido

DOI 10.1103/PhysRevB.64.224511 · Physical Review B

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Abstract

The spectral function for Cooper pair transfer in small metallic superconductors is examined. By performing an exact calculation in a small system, it is shown that a clear evidence of pairing correlations persists in this quantity for temperatures well above the BCS critical temperature, as well as for sizes considerably below the BCS lower size limit for superconductivity. At the same time, however, signatures of the BCS phase transition in small systems remain evident. Differences between even and odd systems are as well analyzed. The number-parity-projected BCS and random-phase approximation treatments of the spectral function at finite temperature are also discussed and compared with the exact results. Their predictions for larger configuration spaces are also shown.