  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.
