Single crystal growth and superconductivity in RbNi$_2$Se$_2$

TL;DR

This study reports the synthesis and detailed characterization of RbNi$_2$Se$_2$, revealing its superconducting properties, multi-gap nature, and electronic structure, contributing to understanding nickel-based superconductors.

Contribution

It is the first comprehensive investigation of RbNi$_2$Se$_2$, demonstrating its superconductivity, multi-band electronic structure, and weak electronic correlations through experiments and calculations.

Findings

Superconducting transition at 1.20 K.

RbNi$_2$Se$_2$ is a multi-gap superconductor.

Exhibits weak electronic correlations and multi-band features.

Abstract

We report the synthesis and characterization of RbNi$_2$Se$_2$, an analog of the iron chalcogenide superconductor Rb$_x$Fe$_2$Se$_2$, via transport, angle resolved photoemission spectroscopy, and density functional theory calculations. A superconducting transition at $T_{c}$ = 1.20 K is identified. In normal state, RbNi$_2$Se$_2$ shows paramagnetic and Fermi liquid behaviors. A large Sommerfeld coefficient yields a heavy effective electron mass of $m^{*}\approx6m_{e}$. In the superconducting state, zero-field electronic specific-heat data $C_{es}$ can be described by a two-gap BCS model, indicating that RbNi$_2$Se$_2$ is a multi-gap superconductor. Our density functional theory calculations and angle resolved photoemission spectroscopy measurements demonstrate that RbNi$_2$Se$_2$ exhibits relatively weak correlations and multi-band characteristics, consistent with the multi-gap superconductivity.