Superconductivity in Ba(TM,Si)2(TM = Pd, Pt, Cu, Ag, and Au) with the AlB2-Type Structure

Abstract

We succeeded in synthesizing BaTM x Si 2- x (TM = Pd, Pt, Cu, Ag, and Au) superconductors with the AlB 2 -type structure and performed detailed thermodynamic measurements of the superconducting state in BaTM x Si 2- x to determine the superconducting parameters [ H c1 (0), H c2 (0), λ(0), ξ(0), and κ GL ] using Ginzburg–Landau relations. The observed parameters indicated that BaTM x Si 2- x can be categorized into a conventional type-II superconductor. The AlB 2 -type structure appears at x between 0.2 and 0.8, and the lattice parameters systematically changed with x . The superconductivity was observed at a TM concentration x = 0.2–0.6. T c was almost constant between x = 0.2 and 0.3 and observed to decrease with increasing TM concentration (0.3 ≤ x ≤0.6). The specific heat data indicated that the superconductivity in BaTM x Si 2- x exists in a weak coupling regime in the BCS theory. Moreover, we discussed the role of the TM element in BaTM x Si 2- x using the observed data.