Single Crystal*

In superconducting material without an inversion center of symmetry the spin degeneracy of the conducting band is lifted by an antisymmetric spin orbit coupling (ASOC). As a consequence, spin and parity cannot be seperately used to classify the Cooper pairing states. The superconducting order parameter is generally a mixture of spin singlet and triplet pairing states. However, such spin mixture state has rarely been revealed in weakly correlated noncentrosymmetrical superconductors. In this talk, we report a pressure-dependent point contact Andreev reflection measurement on high quality single crystals of the noncentrosymmetrical superconductor PbTaSe₂. The experimental result reveals the effects of ASOC on the superconducting order parameter of PbTaSe₂.