Observation of sub-kelvin superconductivity in Cd_3As_2 thin films

We report the first experimental observation of superconductivity in Cd_3As_2 thin films without application of external pressure. Surface studies suggest that the observed transport characteristics are related to the polycrystalline continuous part of investigated films with homogeneous distribution of elements and the Cd-to-As ratio close to stoichiometric Cd_3As_2. The latter is also supported by Raman spectra of the studied films, which are similar to those of Cd_3As_2 single crystals. The formation of superconducting phase in films under study is confirmed by the characteristic behavior of temperature and magnetic field dependence of samples resistances, as well as by the presence of pronounced zero-resistance plateaux in dV/dI characteristics. The corresponding H_c-T_c plots reveal a clearly pronounced linear behavior within the intermediate temperature range, similar to that observed for bulk Cd_3As_2 and Bi_2Se_3 films under pressure, suggesting the possibility of nontrivial pairing in the films under investigation. We discuss a possible role of sample inhomogeneities and crystal strains in the observed phenomena.