Regensburg 2013 – wissenschaftliches Programm
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TT: Fachverband Tiefe Temperaturen
TT 62: Superconductivity: Properties, Electronic Structure, Order Parameter
TT 62.4: Vortrag
Donnerstag, 14. März 2013, 15:45–16:00, H19
Soft-mode enhanced superconductivity in the antiperovskite APt3P, A=Sr, Ca, La — •Rolf Heid and Klaus-Peter Bohnen — Institut für Festkörperphysik, Karlsruher Institut für Technologie
The surprising discovery of superconductivity in iron pnictides initiated an increased search for superconductivity in other unconventional compounds. Recently, a new class of P-based antiperovskites was synthesized, and superconductivity with a Tc of 8.4 K was observed for SrPt3P [1]. Specific heat measurements indicated a strong-coupling scenario and the presence of low-energy phonon modes. Replacing Sr by Ca or La resulted in lower Tc’s and a progressive loss of strong-coupling signatures.
Here we present results of a first principles study of lattice dynamics
and electron-phonon coupling properties of APt3P, A=Sr, Ca,
La, with full consideration of spin-orbit interaction. For SrPt3P,
the coupling is carried almost totally by a single low-frequency branch consisting
of planar Pt vibrations, which result in a coupling constant of λ
≈ 2. In CaPt3P this mode stiffens significantly thereby reducing
λ to about 1, while in LaPt3P the coupling
is further reduced to 0.5 because of a shift of the electronic bands. In contrast to previous work [2,3], our ab initio results
provide a consistent quantitative description of the key features of
superconductivity in this new class of materials within the framework
of the strong-coupling Eliashberg theory.
[1] Takayama et al. PRL 108, 27001 (2012)
Chen et al., PRB 86, 125116 (2012)
Kang et al., arXiv:1207.6196