UC Berkeley

We report the synthesis and characterization of RbNi2Se2, an analog of the iron chalcogenide superconductor RbxFe2Se2, via transport, angle-resolved photoemission spectroscopy, and density functional theory calculations. A superconducting transition at Tc=1.20 K is identified. In the normal state, RbNi2Se2 shows paramagnetic and Fermi-liquid behaviors. A large Sommerfeld coefficient yields an effective electron mass of m∗≈6me. In the superconducting state, zero-field electronic specific-heat data Ces can be described by a two-gap BCS model, indicating that RbNi2Se2 is a possible multigap superconductor. Our density functional theory calculations and angle-resolved photoemission spectroscopy measurements demonstrate that RbNi2Se2 exhibits relatively weak correlations and multiband characteristics, consistent with the multigap superconductivity.