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 $\text{La}{T}_{4}{X}_{12}$ ($T=\text{Ru}$, Pt and $X=\text{P}$, 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 ${\mathrm{LaRu}}_{4}{\mathrm{P}}_{12}$, 1.03 for ${\mathrm{LaRu}}_{4}{\mathrm{As}}_{12}$, and 1.08 for ${\mathrm{LaPt}}_{4}{\mathrm{Ge}}_{12}$. The superconducting critical temperature (${T}_{c}$) values for ${\mathrm{LaRu}}_{4}{\mathrm{P}}_{12}, {\mathrm{LaRu}}_{4}{\mathrm{As}}_{12}$, and ${\mathrm{LaPt}}_{4}{\mathrm{Ge}}_{12}$ 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.