Effect of Co doping on superconductivity and transport properties in SmFe$_{1-x}$Co$_{x}$AsO

TL;DR

This study explores how cobalt doping affects superconductivity and transport properties in SmFeAsO, revealing a dome-shaped $T_c$ dependence on doping and a correlation between thermopower and superconductivity.

Contribution

It provides the first detailed phase diagram of Co-doped SmFeAsO showing the suppression of magnetic order and emergence of superconductivity with a maximum $T_c$ at optimal doping.

Findings

Superconductivity appears for Co doping $x \\geq 0.05$.

Maximum $T_c$ of 17.2 K at $x \\sim 0.10$.

A dome-like $T_c$ versus $x$ curve is established.

Abstract

We investigate superconductivity and transport properties of Co doped SmFe$_{1-x}$Co$_{x}$AsO system. The antiferromagnetic (AFM) spin-density wave (SDW) order is rapidly suppressed by Co doping, and superconductivity emerges as $x$ $\geq$ 0.05. $T_c$$^{mid}$ increases with increasing Co content, shows a maximum of 17.2 K at the optimally doping of $x\sim$ 0.10. A phase diagram is derived based on the transport measurements and a dome-like $T_c$ versus $x$ curve is established. Meanwhile we found that the normal state thermopower might consist of two different contributions. One contribution increases gradually with increasing $x$, and the other contribution is abnormally enhanced in the superconducting window 0.05 $\leq$ $x$ $\leq$ 0.20, and shows a dome-like doping dependence. A close correlation between $T_{c}$ and the abnormally enhanced term of thermopower is proposed.