Synthesizing and characterization of hole doped nickel based superconductor (La$_{1-x}$Sr$_{x}$)NiAsO

TL;DR

This study synthesizes and characterizes hole-doped LaSrNiAsO, revealing increased superconducting transition temperature, multiband conduction, and absence of spin density wave anomalies, advancing understanding of Ni-based superconductors.

Contribution

It introduces hole doping in LaNiAsO, demonstrating enhanced Tc and multiband effects, which were not previously explored in this material.

Findings

Tc increases from 2.4 K to 3.7 K with Sr doping

Normal state resistivity shows metallic behavior without SDW anomaly

Hall measurements reveal a transition from electron to hole conduction with doping

Abstract

We report the synthesizing and characterization of the hole doped Ni-based superconductor ($La_{1-x}Sr_{x})NiAsO$. By substituting La with Sr, the superconducting transition temperature $T_c$ is increased from 2.4 K of the parent phase $LaNiAsO$ to 3.7 K at the doping levels x= 0.1 - 0.2. The curve $T_c$ versus hole concentration shows a symmetric behavior as the electron doped samples $LaNiAs(O_{1-x}F_{x})$. The normal state resistivity in Ni-based samples shows a good metallic behavior and reveals the absence of spin density wave induced anomaly which appears in the Fe-based system at about 150 K. Hall effect measurements indicate that the electron conduction in the parent phase $LaNiAsO$ is dominated by electron-like charge carriers, while with more Sr doping, a hole-like band will emerge and finally prevail over the conduction, such a phenomenon reflects that the Fermi surface of $LaNiAsO$ comprises of electron pockets and hole pockets, thus the sign of charge carriers could be changed once the contribution of hole pockets overwhelms that of electron pockets. Magnetoresistance measurements and the violation of Kohler rule provide further proof that multiband effect dominate the normal state transport of ($La_{1-x}Sr_{x})NiAsO$.