Fluctuating order parameter in doped cuprate superconductors

TL;DR

This paper investigates how static fluctuations of the d-wave superconducting order parameter in doped cuprates relate to quasiparticle scattering, explaining the collapse of critical temperature at high doping levels.

Contribution

It provides a theoretical analysis of order parameter fluctuations and spatial correlations in doped cuprates, linking fluctuations to the suppression of superconductivity.

Findings

Order parameter saturates with doping while fluctuations grow.

Fluctuations can explain the collapse of $T_c$ at overdoping.

Spatial correlations of the order parameter are analyzed.

Abstract

We discuss static fluctuations of the d-wave superconducting order parameter $\Delta$ in CuO$_2$ planes, due to quasiparticle scattering by charged dopants. The analysis of two-particle anomalous Green functions at $T = 0$ permits to estimate the mean-square fluctuation $\delta^2 = <\Delta^2> - <\Delta>^2$, averaged in random dopant configurations, to the lowest order in doping level $c$. Since $\Delta$ is found to saturate with growing doping level while $\delta$ remains to grow, this can explain the collapse of $T_c$ at overdoping. Also we consider the spatial correlations $<\Delta(0)\Delta({\bf R})>$ for order parameter in different points of the plane.