Nonlocal Effect of Local Nonmagnetic Impurity in High-Tc Superconductors: Induced Local Moment and Huge Residual Resistivity

TL;DR

This paper investigates how a strong nonmagnetic impurity affects high-Tc superconductors, revealing that it induces local moments and significantly increases residual resistivity through enhanced susceptibilities and suppressed quasiparticle coherence.

Contribution

It introduces the GVI-FLEX method to analyze impurity effects, providing a unified explanation for impurity-induced phenomena in high-Tc superconductors.

Findings

Enhanced local and staggered susceptibilities around impurities

Suppressed quasiparticle lifetime and local density of states

Huge residual resistivity exceeding s-wave scattering limits

Abstract

We study a Hubbard model with a strong onsite impurity potential based on an improved fluctuation-exchange (FLEX) approximation, which we call the GVI-FLEX method. We find that (i) both local and staggered susceptibilities are strongly enhanced around the impurity. By this reason, (ii) the quasiparticle lifetime as well as the local density of states (DOS) are strongly suppressed in a wide area around the impurity (like a Swiss cheese hole), which causes the ``huge residual resistivity'' beyond the s-wave unitary scattering value. These results by the GVI method naturally explains the various impurity effects in HTSC's in a unified way, which had been a long-standing theoretical problem.