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Modern Physics Letters B

ON THE EFFECTIVE THEORY OF A BCS SYSTEM AT ZERO TEMPERATURE

Adriaan M. J. Schakel

Published Aug 10, 1990• 29 citations
Publisher

Abstract

A microscopic derivation is given of the recently proposed effective action of a BCS-type system at zero temperature.
DOI
10.1142/s021798499000115x

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To investigate the pairing phase transition in finite systems with the particle-number conservation, we formulate a new BCS-type theory at finite temperature, by deriving a set of variational equations of the free energy after the particle-number projection. This theory enables us to distinguish the symmetry-restoring fluctuation (SRF) from additional quantum fluctuations. By numerical calculations, it is found that the phase transition is compatible with the conservation law in this theory, and that the SRF shifts up the critical temperature. Having correct zero-temperature limit, this theory also gives new interpretation on the Pauli blocking effect in systems with odd particle number.