Impurity Substitution in Bismuth and Thallium Cuprates: Suppression of T_c and Estimation of Pseudogap

TL;DR

This study investigates how impurity substitution affects the critical temperature and pseudogap in bismuth and thallium cuprates, providing estimates of pseudogap magnitude and insights into the electronic state changes.

Contribution

It introduces a method to estimate pseudogap magnitude from T_c suppression data using the Abrikosov-Gorkov formalism in cuprates with impurity doping.

Findings

Pseudogap magnitude correlates with the characteristic temperature T* from thermoelectric measurements.

Impurity doping suppresses T_c and influences the density of states and pseudogap.

Susceptibility calculations reveal a broad peak indicating an unusual metallic state at high temperatures.

Abstract

Suppression of T_c in bilayer bismuth and thallium cuprates, by substitution of Co impurities at Cu sites, are taken for examination. T_c suppression data on differently doped Bi2212 and Tl2212 are analysed within the unitary pair-breaking formalism due to Abrikosov and Gorkov, by fitting data points to a phenomenological relation valid for weak coupling d-wave superconductors. Values of the pseudogap magnitude at each doping are thereby estimated within a "fermi-level density of states suppression" picture. Pseudogap magnitude from our estimation is observed to have a correspondence with a related characteristic temperature T^\star obtained by thermoelectric power measurements. Effects of pseudogap, on the density of states, is studied by calculating the susceptibility which shows a broad peak at high temperature. This peak feature in susceptibility is indicative of an unusual metallic state which could further be explored by systematic other measurements.