Peak in the superconducting transition temperature of the nonmagnetic topological line-nodal material CaSb_2 under pressure

摘要

Investigating the pressure dependence of the superconducting (SC) transition temperature T_c is crucial for understanding the SC mechanism. Herein, we report on the pressure dependence of T_c in the nonmagnetic topological line-nodal material CaSb_2 based on measurements of electric resistance and alternating current magnetic susceptibility. T_c initially increases with increasing pressure and peaks at ～ 3.1 GPa. With a further increase in pressure, T_c decreases and finally becomes undetectable at 5.9 GPa. Because no signs of phase transition or Lifshitz transition are observed in the normal state, the peculiar peak structure of T_c suggests that CaSb_2 has an unconventional SC character.