Superconductivity in the Platinum GermanidesMPt4Ge12(M=Rare−Earth

Abstract

New germanium-platinum compounds with the filled-skutterudite crystal structure were synthesized. The crystal structure and composition were investigated by x-ray diffraction and microprobe analysis. Magnetic susceptibility, specific heat, and electrical resistivity measurements evidence superconductivity in LaPt4Ge12 and PrPt4Ge12 below 8.3 K. The parameters of the normal and superconducting states were established. Strong coupling and a crystal electric field singlet ground state is found for the Pr compound. Electronic structure calculations show a large density of states at the Fermi level. Similar behavior with lower Tc was observed for SrPt4Ge12 and BaPt4Ge12.

Comparative photoemission studies on the superconducting gap of the filled skutterudite superconductors LaPt4Ge12and PrPt4Nakamura1, Okazaki2, Yoshida3 et al. 2012Phys. Rev. B246221View full textAdd to dashboardCite

“…17 We estimate (0) to be 1.4 meV by extrapolating the observed gap magnitude and assuming a temperature dependent gap. This corresponds to a reduced gap value 2 (0)/k B T c of 3.9 ± 0. gap value also agrees well with the values determined from the specific heat measurements [2 (0)/k B T c = 3.88], 5 indicating that PES is a reliable experimental tool for studying the superconducting gap in this new filled skutterudite superconductor. The value for the LaPt 4 Ge 12 fit is larger than those for elemental metals 18 but comparable to that for LaRu 4 P 12 (T c = 7.2 K), where the value was discussed in relation to possible superconducting gap anisotropy.…”

“…According to band structure calculations, the states near the E F of LaPt 4 Ge 12 and PrPt 4 Ge 12 have a dominant Ge 4p character hybridized with Pt 5d. 5 Resonant PES studies of PrPt 4 Ge 12 do not show significant enhancement of the spectral intensity near E F across the Pr 3d-to-4f threshold, 14 in contrast with similar studies of PrFe 4 P 12 , which is considered to be a heavy fermion material with significant hybridization of the conduction band and 4f electrons. 15 The spectrum at 4K (the superconducting state) of each compound shows a reduced intensity near the E F region and a peak at 2 meV.…”

“…PrPt 4 Ge 12 is a newly synthesized filled skutterudite compound with a Pt-Ge framework [4][5][6][7] (Fig. 1) with a superconducting transition temperature T c of 7.9 K, 5 which is unexpectedly high among similar Pr-based superconductors.…”

Weak interband-coupling superconductivity in the filled skutteruditeLaPt4Ge12

“…A family of Ge-based skutterudites with T c ranging from 5 to 8.3 K , i.e., M Pt 4 Ge 12 (M =Sr, Ba, La, Pr), was discovered a few years ago [7][8][9][10]. Resembling those of PrOs 4 Sb 12 , zero-field µSR experiments showed evidence of time-reversal symmetry (TRS) breaking in the superconducting state of PrPt 4 Ge 12 , but not for LaPt 4 Ge 12 [11][12][13].…”

“…The µSR experiments were performed at the Paul Scherrer Institute (Switzerland) at the πM3 beam line on the GPS spectrometer down to 1.5 K and at the LTF spectrometer down to T ≈ 0.02 K on polycrystalline LaPt 4 Ge 12 samples [7]. The samples were cooled in B app = 75 mT from above T c down to 1.5 K, and then measured as a function of temperature.…”