Filamentary superconductivity in semiconducting policrystalline ZrSe2 compound with Zr vacancies

ZrSe2 is a band semiconductor studied long time ago. It has interesting electronic properties, and because its layers structure can be intercalated with different atoms to change some of the physical properties. In this investigation we found that Zr deficiencies alter the semiconducting behavior and the compound can be turned into a superconductor. In this paper we report our studies related to this discovery. The decreasing of the number of Zr atoms in small proportion according to the formula ZrxSe2, where x is varied from about 8.1 to 8.6 K, changing the semiconducting behavior to a superconductor with transition temperatures ranging between 7.8 to 8.5 K, it depending of the deficiencies. Outside of those ranges the compound behaves as semiconducting with the properties already known. In our experiments we found that this new superconductor has only a very small fraction of superconducting material determined by magnetic measurements with applied magnetic field of 10 Oe. Our conclusions is that superconductivity is filamentary. However, in one studied sample the fraction was about 10.2 %, whereas in others is only about 1 % or less. We determined the superconducting characteristics; the critical fields that indicate a type two superonductor with Ginzburg-Landau ? parameter of the order about 2.7. The synthesis procedure is quite normal fol- lowing the conventional solid state reaction. In this paper are included, the electronic characteristics, transition temperature, and evolution with temperature of the critical fields.
Comment: Accepted in J of superconductivity and novel magnetism