Doping Dependence of Superconductivity and Lattice Constants in Hole Doped $La_{1-x}Sr_xFeAsO$

TL;DR

This study demonstrates that hole doping in LaFeAsO via Sr substitution enhances superconductivity and lattice constants, showing a symmetric behavior with electron doping, and provides insights into doping effects on superconducting properties.

Contribution

It reveals the doping dependence of superconductivity and lattice parameters in hole-doped LaFeAsO, highlighting the symmetric behavior with electron doping.

Findings

Superconducting transition temperature $T_c$ increases with hole doping.

Lattice constants (a-axis and c-axis) expand with hole doping.

Superconductivity can be induced by hole doping through Sr substitution.

Abstract

By using solid state reaction method we have fabricated the hole doped $La_{1-x}Sr_xFeAsO$ superconductors with Sr content up to 0.13. It is found that the sharp anomaly at about 150 K and the low temperature upturn of resistivity are suppressed by doping holes into the parent phase. Interestingly both the superconducting transition temperature $T_c$ and the lattice constants (a-axis and c-axis) increase monotonously with hole concentration, in sharp contrast with the electron doped side where the $T_c$ increases with a continuing shrinkage of the lattice constants either by dope more fluorine or oxygen vacancies into the system. Our data clearly illustrate that the superconductivity can be induced by doping holes via substituting the trivalent La with divalent Sr in the LaFeAsO system with single FeAs layer, and the $T_c$ in the present system exhibits a symmetric behavior at the electron and hole doped sides, as we reported previously.