Quasi-two-dimensional Fermi surface of superconducting line-nodal metal CaSb₂

Abstract

We report on the Fermi surfaces and superconducting parameters of CaSb₂ single crystals (superconducting below Tc ~ 1.8 K) grown by the self-flux method. The frequency of de Haas–van Alphen and Shubnikov–de Haas oscillations evidences a quasi-two-dimensional (quasi-2D) Fermi surface, consistent with one of the Fermi surfaces forming Dirac lines predicted by first-principles calculations. Measurements in the superconducting state reveal that CaSb₂ is close to a type-I superconductor with the Ginzburg-Landau parameter of around unity. The temperature dependence of the upper critical field Hc₂ is well described by a model considering two superconducting bands, and the enhancement of the effective mass estimated from Hc₂(0K) is consistent with the quasi-2D band observed by the quantum oscillations. Our results indicate that a quasi-2D band forming Dirac lines contributes to the superconductivity in CaSb₂.