Evolution of the superconducting transition temperature upon a substitution of Pd by Pt in Li2(Pd1-xPtx)3B (x = 0-1)

Abstract

We investigate on the evolution of the superconducting transition temperature upon a substitution of Pd by Pt in the noncentrosymmetric superconductor Li2(Pd1-xPtx)3B. The spin singlet and spin triplet superconducting states can coexist in noncentrosymmetric crystal structures like Li2T3B (T=Pt, Pd), while it is prohibited in ordinary crystal structures. This study is conducted to investigate the crossover nature in Li2 (Pd1-xPtx) 3B (x = 0-1) for obtaining information on the parity mixing. We have succeeded in synthesizing samples which have higher Tc than previous results around x = 1. A lot of samples have been synthesized with different ratios of x, and we found that the value of Tc changed continuously and there was no clear discontinuity between spin singlet dominant (x~0) and spin triplet dominant (x~1) state in Tc value, although the x dependence of Tc is decreasing nonlinearly with the increase of x. The higher x region around x~0.8 seems to be suppressed from linear behaviour.