Emergence of superconductivity in partially substituted ZrTe_2-xSe_x (x < 0.3) single crystals

Transition metal dichalcogenides (MX₂), where M is a transition metal and X is a chalcogen (S, Se, or Te), typically exhibit low-dimensional structures with intercalated metal and chalcogen layers. These materials demonstrate diverse ground states, including superconductivity and "Charge Density Wave" (CDW) phenomena. Pristine ZrTe₂ is not a superconductor and is classified as a Dirac semimetal, featuring Dirac cones that connect at specific points in reciprocal space. This study investigates the effects of substituting Se for Te in ZrTe_2-xSe_x, focusing on the emergence of superconductivity. Single crystals of ZrTe_2-xSe_x were synthesized using the Isothermal Chemical Vapor Transport (ICVT) method, which employs chemical potential differences for crystallization. Electrical resistance measurements revealed superconducting states at low temperatures, with an optimal transition temperature (T_C) of 4.7 K for ZrTe_1.85Se_0.15, and a dome-like feature in the T_C vs. x phase diagram. These findings indicate that small atomic substitutions are more effective than chalcogen defects in inducing superconductivity on ZrTe₂. Given ZrTe₂'s topological electronic structure, the superconductivity in ZrTe_2-xSe_x may have implications for quantum computing.