Superconducting properties of lanthanum selenide

Superconductivity phenomena in lanthanum selenide crystals with different electron concentration are observed. The parameters describing the superconducting state, in particular the critical temperature T c and the lower critical field H cl , are determined from measurements of the resistivity transition, the magnetic susceptibility and the Meissner effect on samples with various electron concentrations. From the experimental results the Ginzburg‐Landau parameter χ, the penetration depth λ d , coherence length ξ d , the Gorkov impurity parameter ϱ, etc. are deduced. The dependence of the critical temperature T c on electron concentration is calculated on the basis of McMillan's theory and compared with experiment.