Abstract

The physical properties of CsNi2Se2 were characterized by electrical resistivity, magnetization and specific heat measurements. We found that the stoichiometric CsNi2Se2 compound undergoes a superconducting transition at Tc = 2.7 K. A large Sommerfeld coefficient (∼77.90 mJ/mol K−2) was obtained from the normal state electronic specific heat. However, the Kadowaki–Woods ratio of CsNi2Se2 was estimated to be about 0.041 × 10cm(mol K2/mJ)2, indicating the absence of strong electron–electron correlations. In the superconducting state, we found that the zero-field electronic specific heat data, Ces(T) (0.5 K T < 2.7 K), can be fitted well with a two-gap BCS model, indicating the multi-gap feature of CsNi2Se2. The comparison with the density functional theory (DFT) calculations suggested that the large in these nickel selenide superconductors may be related to the large density of states (DOS) at the Fermi surface.

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