Electron-phonon superconductivity in the filled skutterudites LaRu4P12, LaRu4As12, and LaPt4Ge12

Abstract

We have reported on the structural, elastic, electronic, lattice dynamical and electron-phonon interaction properties of LaT4X12 (T = Ru, Pt and X = P, As, Ge) by using the generalized gradient approximation of the density functional theory and the plane-wave pseudopotential method. These lanthanum-filled skutterudites are found to be characterized with a flat band, resulting in a sharp peak in the electronic density of states, near the Fermi level. The lattice dynamical properties of these materials change considerably when the P atom is replaced by larger As or Ge atoms. The Migdal-Eliashberg approach is used to determine the Eliashberg spectral function for all the considered compounds. Using the calculated Eliashberg spectral function, the value of average electron-phonon coupling parameter is found to be 0.74 for LaRu4P12, 1.03 for LaRu4As12, and 1.08 for LaPt4Ge12. The superconducting critical temperature (T-c) values for LaRu4P12, LaRu4As12, and LaPt4Ge12 are estimated to be 6.95, 11.56, and 8.32 K, respectively, which compare well enough with their experimentally measured values of 7.2, 10.45, and 8.23 K.