Phys. Rev. B 55, 15153–15156 (1997)BCS to Bose crossover: Broken-symmetry stateReceived 26 December 1995; published in the issue dated 1 June 1997 A functional integral formulation, used previously to calculate Tc and describe normal state properties of the BCS-Bose crossover, is extended to T<Tc. The saddle point approximation is shown to be qualitatively correct for T≪Tc for all couplings, in contrast to the situation above Tc. Several features of the crossover are described. The difference between the T=0 ``pair size'' and the (prefactor of the T dependent) Ginzburg-Landau coherence length is pointed out: the two quantities are the same only in the BCS limit. The evolution of the collective modes from the BCS to the Bose regime is discussed together with the mixing of the amplitude and phase in the absence of a particle-hole symmetry. © 1997 The American Physical Society URL:
http://link.aps.org/doi/10.1103/PhysRevB.55.15153
DOI:
10.1103/PhysRevB.55.15153
PACS:
74.20.-z, 67.40.-w, 74.40.+k, 74.72.-h
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