Theory for underdoped high-T_c superconductors: effects of phase fluctuations

TL;DR

This paper develops a theoretical extension of the FLEX approximation to include phase fluctuations, explaining the observed scaling of T_c with superfluid density in underdoped high-T_c superconductors.

Contribution

The authors extend the FLEX approximation to self-consistently incorporate phase fluctuations, providing a better understanding of T_c behavior in underdoped cuprates.

Findings

T_c scales with superfluid density n_s in underdoped cuprates

Standard FLEX fails to predict T_c scaling without phase fluctuations

Extended FLEX captures the influence of phase fluctuations on T_c

Abstract

In underdoped cuprates, T_c is thought to be determined by Cooper pair phase fluctuations because of the small superfluid density n_s. Experimentally, T_c is found to scale with n_s. The fluctuation-exchange approximation (FLEX) in its standard form fails to predict this behavior of T_c since it does not include phase fluctuations. We therefore extend the FLEX to include them selfconsistently. We present results for T_c[n_s,x], where x is the doping.