Phase fluctuations and pseudogap properties: influence of nonmagnetic impurities

The presence of nonmagnetic impurities in a 2D "bad" metal depresses the su perconducting Berezinskii-Kosterlitz-Thouless transition temperature while leaving the pairing energy scale unchanged. Thus the region of the pseudoga p nonsuperconducting phase, in which the modulus of the order parameter is nonzero but its phase is random and which arises at the pairing temperature , is substantially bigger than for the clean system. This supports the prem ise that fluctuations in the phase of the order parameter can in principle describe the pseudogap phenomena in high-T-c materials over a rather wide r ange of temperatures and carrier densities. The temperature dependence of t he bare superfluid density is also discussed. (C) 2000 American Institute o f Physics. [S1063-777X(00)00606-X].