Low temperature specific heat of ternary germanide superconductor La 3Pd 4Ge 4

Abstract

Low temperature specific heat measurements are performed in a novel ternary superconductor La 3Pd 4Ge 4, which forms U 3Ni 4Si 4-type crystal structure consisting of the combination of alternating units of AlB 2- and BaAl 4 (ThCr 2Si 2)-type layers. The Sommerfeld coefficient γ n = 27.0 mJ / mol K 2 and the Debye temperature Θ D = 256 K are derived from the normal state specific heat. The electron–phonon coupling constant and the electronic density of states at the Fermi level are also derived. Temperature dependence of the superconducting electronic specific heat is well described by the BCS exponential behavior with gap Δ 0 = 0.30 meV . The results suggest La 3Pd 4Ge 4 has fully opened isotropic gap in the superconducting state.