Phase Fluctuations and Pseudogap Properties: Influence of Nonmagnetic Impurities

TL;DR

This paper investigates how nonmagnetic impurities affect the pseudogap and superconducting transition in a 2D system, showing impurities expand the pseudogap region by suppressing phase coherence without changing pairing energy.

Contribution

It demonstrates that nonmagnetic impurities depress the BKT transition temperature while leaving the pairing energy unchanged, supporting phase fluctuation models for the pseudogap in high-$T_c$ materials.

Findings

Pseudogap region enlarges with impurities due to suppressed phase coherence.

Superfluid density's temperature dependence is analyzed.

Superconducting transition temperature decreases with impurity concentration.

Abstract

The presence of nonmagnetic impurities in a 2D ``bad metal'' depresses the superconducting Berezinskii-Kosterlitz-Thouless transition temperature, while leaving the pairing energy scale unchanged. Thus the region of the pseudogap non-superconducting phase, where the modulus of the order parameter is non-zero but its phase is random, and which opens at the pairing temperature is substantially bigger than for the clean system. This supports the premise 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 range of temperatures and carrier densities. The temperature dependence of the bare superfluid density is also discussed.