The physical properties of CsNi$_{2}$Se$_{2}$ were characterized by electrical resistivity, magnetization and specific heat measurements. We found that the stoichiometric CsNi$_{2}$Se$_{2}$ compound is a superconductor with a transition temperature textit{T$_{c}$}=2.7K. A large Sommerfeld coefficient $gamma$$_{n}$ ($sim$77.90 mJ/mol$cdot$K$^{-2}$), was obtained from the normal state electronic specific heat. However, the Kadowaki-Woods ratio of CsNi$_{2}$Se$_{2}$ was estimated to be about 0.041$times$10$^{-5}$ $muOmega$$cdot$cm(mol$cdot$K/mJ)$^{2}$, indicating the absence of strong electron-electron correlations in this compound. In the superconducting state, we found that the zero-field electronic specific heat data, $C_{es}(T)$ (0.5K $leq$ T $<$ 2.6K), can be well fitted with a two-gap BCS model. The comparison with the results of the density functional theory (DFT) calculations suggested that the large $gamma$$_{n}$ in the nickel-selenide superconductors may be related to the large Density of States (DOS) at the fermi surface.
Download