Stability of condensate in superconductors

TL;DR

This paper demonstrates that the superconducting condensate remains stable by separating condensed and noncondensed Cooper pairs with an energy gap, supporting the fundamental assumptions of BCS theory.

Contribution

It introduces a mechanism showing how the condensate inhibits noncondensed pairs, confirming the stability of the BCS condensate against two-particle excitations.

Findings

Condensed and noncondensed Cooper pairs are separated by a specific energy gap.

The energy gap prevents nucleation of noncondensed pairs in other modes.

The results justify the basic assumptions of BCS theory regarding condensate stability.

Abstract

According to the BCS theory the superconducting condensate develops in a single quantum mode and no Cooper pairs out of the condensate are assumed. Here we discuss a mechanism by which the successful mode inhibits condensation in neighboring modes and suppresses a creation of noncondensed Cooper pairs. It is shown that condensed and noncondensed Cooper pairs are separated by an energy gap which is smaller than the superconducting gap but large enough to prevent nucleation in all other modes and to eliminate effects of noncondensed Cooper pairs on properties of superconductors. Our result thus justifies basic assumptions of the BCS theory and confirms that the BCS condensate is stable with respect to two-particle excitations.