Regensburg 2007 – scientific programme
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TT: Fachverband Tiefe Temperaturen
TT 10: Superconductivity - Properties, Electronic Structure, Order Parameter
TT 10.12: Talk
Tuesday, March 27, 2007, 12:30–12:45, H18
Thermodynamic and Transport Properties of the Noncentrosymmetric Superconductor LaBiPt — •Gernot Goll1, Michael Marz1, Andreas Hamann1, Tihomir Tomanic1, Kai Grube2, T. Yoshino3, and T. Takabatake3 — 1Physikalisches Institut, Universität Karlsruhe, 76128 Karlsruhe — 2Forschungszentrum Karlsruhe, Institut für Festkörperphysik, 76021 Karlsruhe — 3Hiroshima University, Higashi-Hiroshima, Japan
Noncentrosymmetric superconductors have attracted considerable interest in recent years. The lack of an inversion center of the crystal lattice makes unconventional pairing symmetries feasible. Even mixed superconducting states consisting of singlet and triplet states are possible. We report on the observation of superconductivity in the half-Heusler compound LaBiPt which crystallizes in the noncentrosymmetric cubic space group F43m. The crystal structure is composed of three fcc sublattices for Pt, Bi, and La with the relative atomic coordinates (0,0,0), (1/4,1/4,1/4), and (3/4,3/4,3/4), respectively. LaBiPt becomes superconducting below Tc≈ 0.9 K as evidenced from measurements of the resistivity, magnetisation and specific heat. In view of a simplified BCS model Tc∼ TDexp(−(N(0)V)−1) where N(0)∼ m∗n1/3 is the electronic density of states at the EF, TD is the Debye temperature, and V is the effective, attractive potential, is surprisingly high because LaBiPt is a semimetal with very low charge-carrier concentrations n=6· 1018 cm−3. The carrier concentration is still 1-2 orders of magnitude lower than in the classical low-carrier-density superconductors GeTe and SnTe and comparable to that found in SrTiO3.