Large spin-orbit splitting and weakly anisotropic superconductivity revealed with single-crystalline noncentrosymmetric CaIrSi ₃

We report normal and superconducting properties of the Rashba-type noncentrosymmetric compound CaIrSi ₃ using single crystalline samples with nearly 100% superconducting volume fraction. The electronic density of states revealed by the hard x-ray photoemission spectroscopy can be well explained by the relativistic first-principles band calculation. This indicates that strong spin-orbit interaction indeed affects the electronic states of this compound. The obtained H-T phase diagram exhibits only approximately 10% anisotropy, indicating that the superconducting properties are almost three dimensional. Nevertheless, strongly anisotropic vortex pinning is observed.