Parity and finite size effects in the thermodynamics of small superconductors

R. ROSSIGNOLI; J.P. ZAGORODNY; N. CANOSA

PHYSICS LETTERS A

ELSEVIER SCIENCE BV

Lugar: Amsterdam; Año: 1999 vol. 258 p. 188 - 194

0375-9601

The effects of thermal and quantal gap fluctuations in small superconductors are investigated by means of the static path plus random phase approximation to the partition function, which is implemented in an ensemble with fixed particle number parity NP.. The transitions of the NP projected BCS approximation, examined in detail, become increasingly washed out as the size decreases. Moreover, non-vanishing pairing correlations are seen to subsist in small systems where no ordinary superconducting solution exists at the BCS level. Comparison with exact canonical results obtained for a very small size confirm the predictions obtained with the present method.