We grew high-quality single crystals of the pyrite-type compounds CuS2 and CuSe2 under a pressure of 5 GPa and studied their superconducting and Fermi surface properties by measuring their electrical resistivity, specific heat, and de Haas–van Alphen (dHvA) effect. The upper critical field Hc2 at 0 K [Hc2(0)] is found to be small, Hc2(0) = 160 Oe in CuS2 with the superconducting transition temperature Tsc of 1.5 K and Hc2(0) = 610 Oe in CuSe2 with Tsc of 2.4 K. The detected dHvA branches are small in number in CuS2, but the main dHvA branches, which are expected to exist in the energy band calculations, are hardly observed in CuSe2. The cyclotron effective masses are not large, ranging from 0.8 to 2.4 m0, revealing that the correlation between Cu-3d conduction electrons is weaker than those of the other pyrite-type compounds of the ferromagnet CoS2 and the Mott–Hubbard insulator NiS2.
ASJC Scopus subject areas
- Physics and Astronomy(all)