Superconductivity induced by Ni doping in BaFe$_2$As$_2$

TL;DR

This study reports the discovery of superconductivity in BaFe$_{2-x}$Ni$_x$As$_2$ single crystals, showing a dome-shaped dependence of transition temperature on Ni doping, with maximum $T_c$ of 20.5 K at optimal doping.

Contribution

It demonstrates that Ni doping induces superconductivity in BaFe$_2$As$_2$, providing new insights into electron doping effects in 122 iron-based superconductors.

Findings

Superconductivity appears with Ni doping, peaking at 20.5 K.

Superconducting transition temperature exhibits a dome-like doping dependence.

Electron-like charge carriers dominate in the normal state.

Abstract

A series of 122 phase BaFe$_{2-x}$Ni$_x$As$_2$ ($x$ = 0, 0.055, 0.096, 0.18, 0.23) single crystals were grown by self flux method and a dome-like Ni doping dependence of superconducting transition temperature is discovered. The transition temperature $T_c^{on}$ reaches a maximum of 20.5 K at $x$ = 0.096, and it drops to below 4 K as $x$ $\geq$ 0.23. The negative thermopower in the normal state indicates that electron-like charge carrier indeed dominates in this system. This Ni-doped system provides another example of superconductivity induced by electron doping in the 122 phase.