Physical properties and superconductivity of SrTa2S5

Abstract

SrTa2S5 is revealed to be a BCS superconductor with bulk superconducting transition temperature Tc = 2.27(3) K, as determined from specific heat. The superconducting transition from electrical resistivity ρ measurements is 2.40(16) K; the slightly higher value is associated with filamentary superconductivity. Intergranular conductivity dominates ρ, as surmised from its large magnitude (ρ(3 K) = 454 μΩ cm). The magnetic susceptibility is paramagnetic and temperature independent with a large Van Vleck contribution (estimated at χVV = 1.93(2)x10−4 cm3/mol); below Tc the Meissner effect is observed. Hall effect measurements show that the majority charge carriers are holes with charge-carrier concentration n(5 K) = 2.75(15) × 1020 cm−3. The electronic specific heat coefficient is observed to be γ = 7.62(14) mJ/mol K2. The energy gap associated with the superconducting state is found to be Eg = 0.575(15) meV. Measurements of ρ(T) in magnetic field allow an estimate of the superconducting coherence length ξ ∼ 3.3 Å. SrTa2S5 is classified as a Type II BCS superconductor.