Theoretical analysis of Cooper-pair phase fluctuations in underdoped cuprates: a spin-fluctuation exchange study

Abstract

We study Cooper-pair phase fluctuations in cuprate superconductors for a spin fluctuation pairing interaction. Using an electronic theory we calculate in particular for the underdoped cuprate superconductors the superfluid density $n_s(T)$, the superconducting transition temperature $T_c(x)\propto n_s$ below which phase coherent Cooper-pairs occur, and $T_c^{\ast }(x)$ where the phase incoherent Cooper-pairs disappear. Also we present results for the penetration depth $\lambda (x,T)$ and for the weak pseudogap temperature $T^{\ast }(x)$ at which a gap structure occurs in the spectral density. A Meißner effect is obtained only for $T<T_c$. We find that phase fluctuations become increasingly important in the underdoped regime and lead to a reduction of $T_c$ in good agreement with the experimental situation.

4 pages, 5 figures. One reference added