High-Temperature and High-Pressure Synthesis and Characterization of CuTe₂ Single Crystal

The 3d transition metal dichalcogenide MX₂ (M=Mn, Fe, Co, Ni, Cu, Zn; X=S, Se, Te) with pyrite structure has attracted widespread attention due to their novel physical properties. Among them, the CuX₂ (X=S, Se, and Te) is the only known superconducting system, for which the superconducting transition temperatures (T_c) are 1.5 K (CuS₂), 2.4 K (CuSe₂) and 1.3 K (CuTe₂), respectively. Because they can only be synthesized under high-pressure and high-temperature (HPHT) conditions, earlier reports on CuTe₂ are based on the polycrystalline samples and the detailed physical properties have not been reported on single crystal so far. Here, we synthesized high-quality CuTe₂ single crystals under HPHT conditions at 5 GPa and 900 ℃ using the Kawai type 6/8 two-stage multianvil apparatus and performed detailed crystal, transport, magnetism, and specific heat measurements on its physical properties. The results showed that it belongs to the weakly coupled type-Ⅱ superconductor with T_c about 1.3 K. We systematically compared the relevant superconducting parameters of CuS₂, CuSe₂, and CuTe₂ and further revealed the relationship between their density of state near the Fermi surface and superconducting properties.