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

H. M. Tütüncü

¹

,

Ertuğrul Karaca

²

,

G. P. Srivastava

³

Abstract

We have reported on the structural, elastic, electronic, lattice dynamical and electron-phonon interaction properties of LaT 4 X 12 (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 LaRu 4 P 12 , 1.03 for LaRu 4 As 12 , and 1.08 for LaPt 4 Ge 12 . The superconducting critical temperature (T c ) values for LaRu 4 P 12 , LaRu 4 As 12 , and LaPt 4 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.

Theoretical investigation of superconductivity mechanism in the filled skutterudites YRu4P12, YOs4P12, LaOs1P12 and LaOs4As12

“…In the light of these results, we can suggest that Ru d and P p states dominate the conductivity of this filled skutterudite. It is worth to note that a similar observation has been made for LaRu 4 P 12 in our previous ab initio calculations [29].…”

“…Filled skutterudite pnictides with the general formula LnT 4 X 12 (Ln = Lanthanide, T = Transition metal, X = Pnictogen) have received great attention since they exhibit a variety of individual properties, such as semiconducting [1][2][3][4], metal-insulator transition [5][6][7][8], different magnetic ordering [9][10][11][12][13][14], good thermoelectricity [15][16][17][18], heavy fermion behavior [19,20] and topological insulator behavior [21,22]. Furthermore, the La-based skutterudite compounds have received special interest due to their superconducting properties [23][24][25][26][27][28][29]. In particular, LaOs 4 P 12 and LaOs 4 As 12 exhibit superconductivity below 2.0 and 3.2 K, respectively [23,25].…”

First-principles study of the electronic structure and the Fermi surface in rare-earth filled skutterudites RPt4Ge12

“…Although these compounds have two electron-like and one holelike FS in common, independently of the theoretical scenario used, the hole pockets at Γ point are dependent on the theoretical scenario we used in our calculations. Thus, comparison of our theoretical predictions with de Hass van Alphen [70][71][72] experiments for LaPt 4 Ge 12 and PrPt 4 Ge 12 27 and new experiments for CePt 73 showed that these compounds are phonon-mediated superconductors. Thus, besides the average electron-phonon coupling in lanthanum filled-skutterudite 73 , it would be interesting to calculate electron-phonon couplings for each FS in other filled-skutterudite compound.…”

“…Thus, comparison of our theoretical predictions with de Hass van Alphen [70][71][72] experiments for LaPt 4 Ge 12 and PrPt 4 Ge 12 27 and new experiments for CePt 73 showed that these compounds are phonon-mediated superconductors. Thus, besides the average electron-phonon coupling in lanthanum filled-skutterudite 73 , it would be interesting to calculate electron-phonon couplings for each FS in other filled-skutterudite compound.…”

“…Multi-band pairing with one nodeless and one nodal gap has been inferred 47 leave open the possibility of nodal versus multi-band superconductivity. 73 Ge nuclear quadrupole resonance 49 shows a coherence peak below pairing transition temperature, typical of BCS pairing.…”