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

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 $m^{\ast }\approx 6m_e$. 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.

7 pages, 4 figures

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