Superconductivity and Physical Properties of CaPd2Ge2 Single Crystals

Abstract

We present the superconducting and normal state properties of CaPd2Ge2 single crystal investigated by magnetic susceptibility χ, isothermal magnetization M, heat capacity C_p, in-plane electrical resistivity ρand London penetration depth λversus temperature T and magnetic field H measurements. Bulk superconductivity is inferred from the ρ(T) and C_p(T) data. The ρ(T) data exhibit metallic behavior and undergoes a superconducting transition with T_c onset = 1.98 K and zero resistivity state at T_c 0 = 1.67 K. The χ(T) reveal the onset of superconductivity at 2.0 K. For T>2.0 K, the χ(T) and M(H) are weakly anisotropic paramagnetic with χ_ab > χ_c. The C_p(T) confirm the bulk superconductivity below T_c = 1.69(3) K. The superconducting state electronic heat capacity is analyzed within the framework of a single-band α-model of BCS superconductivity and various normal and superconducting state parameters are estimated. Within the α-model, the C_p(T) data and the ab plane λ(T) data consistently indicate a moderately anisotropic s-wave gap with Δ(0)/k_B T_c ~ 1.6, somewhat smaller than the BCS value of 1.764. The relationship of the heat capacity jump at T_c and the penetration depth measurement to the anisotropy in the s-wave gap is discussed.