Impurity Doping Effect in High $T_{c}$ Superconductors

TL;DR

This paper investigates how impurity doping affects the critical temperature in high-temperature superconductors, using a theory based on weak localization effects to explain experimental observations across different impurity types.

Contribution

The study introduces a theoretical model linking impurity-induced scattering to changes in $T_{c}$, providing a quantitative explanation for experimental data in doped cuprates.

Findings

Impurity doping generally reduces $T_{c}$ in La-based cuprates.

The theoretical model aligns well with experimental data for most impurities.

Ni doping may enhance pairing, deviating from the general trend.

Abstract

It has been observed that impurity doping and/or ion-beam-induced damage in high $T_{c}$ superconductors cause a metal-insulator transition and thereby suppress the critical temperature. Based on our recent theory of the weak localization effect on superconductivity, we examine the variation of $T_{c}$ with increasing of impurity concentration $\rm (x)$ in $\rm{La_{1.85}Sr_{0.15}Cu_{1-x}A_{x}O_{4}}$ systems, where A $=$ Fe, Co, Ni, Zn, or Ga. We find that the doping impurity decreases the scattering matrix elements for electron-electron attractions, such as $V_{nn'}=-V[1-{2\over \pi k_{F}\ell} ln(L/\ell)]$, where $L$ and $\ell$ are the inelastic and elastic mean free paths, respectively. Using the mean free path $\ell$ determined from resistivity data, we find good agreements between our calculated values for $T_{c}$ and experimental data except for Ni-doped samples, where Ni impurities may enhance the pairing interaction.