Reduction of Tc due to Impurities in Cuprate Superconductors

TL;DR

This paper investigates how non-magnetic impurities influence the superconducting transition temperature (Tc) in cuprates, revealing a cancellation effect that explains the Tc reduction and highlighting the role of pseudogap phenomena in underdoped materials.

Contribution

It introduces a detailed theoretical analysis of impurity effects on Tc using the Hubbard model and FLEX approximation, including the impact of pseudogap phenomena on Tc suppression.

Findings

Tc reduction roughly follows Abrikosov-Gor'kov formula

Cancellation between reduced attractive force and damping rate

Pseudogap breaking suppresses Tc reduction in underdoped cuprates

Abstract

In order to explain how impurities affect the unconventional superconductivity, we study non-magnetic impurity effect on the transition temperature using on-site U Hubbard model within a fluctuation exchange (FLEX) approximation. We find that in appearance, the reduction of Tc roughly coincides with the well-known Abrikosov-Gor'kov formula. This coincidence results from the cancellation between two effects; one is the reduction of attractive force due to randomness, and another is the reduction of the damping rate of quasi-particle arising from electron interaction. As another problem, we also study impurity effect on underdoped cuprate as the system showing pseudogap phenomena. To the aim, we adopt the pairing scenario for the pseudogap and discuss how pseudogap phenomena affect the reduction of Tc by impurities. We find that 'pseudogap breaking' by impurities plays the essential role in underdoped cuprate and suppresses the Tc reduction due to the superconducting (SC) fluctuation.