Superconductivity in CaSn3 single crystals with a AuCu3-type structure

Abstract

We report the superconductivity of CaSn₃ single crystals with a AuCu₃-type structure, namely cubic space group Pmm. The superconducting transition temperature T_C = 4.2 K is determined by the magnetic susceptibility, electrical resistivity, and heat capacity measurements. The magnetization versus magnetic field (M–H) curve at low temperatures shows a typical-II superconducting behavior. The estimated lower and upper critical fields are about 125 Oe and 1.79 T, respectively. The penetration depth λ(0) and coherence length ξ(0) are calculated to be approximately 1147 nm and 136 nm by the Ginzburg–Landau equations. The estimated Sommerfeld coefficient of the normal state γ_N is about 2.9 mJ mol⁻¹ K⁻². ΔC/γ_NT_C = 1.13 and λ_ep = 0.65 suggest that the CaSn₃ single crystal is a weakly coupled superconductor. Electronic band structure calculations show a complex multi-sheet Fermi surface formed by three bands and a low density of states (DOSs) at the Fermi level, which is consistent with the experimental results. Based on the analysis of electron–phonon coupling of AX₃ compounds (A = Ca, La, and Y; X = Sn and Pb), we theoretically proposed a way to increase T_C in the system.