Weak interband-coupling superconductivity in the filled skutterudite LaPt4Ge12

Abstract

The superconducting pairing state of LaPt4Ge12 is studied by measuring the magnetic penetration depth λ(T,B) and superfluid density ρs(T) using a tunnel-diode-oscillator (TDO)-based method and transverse-field muon-spin rotation (TF−μSR) spectroscopy. The penetration depth follows an exponential-type temperature dependence at T≪Tc, but increases linearly with magnetic field at T=1.5 K. A detailed analysis demonstrates that both λL(T) and ρsTDO(T), measured in the Meissner state using the TDO method, are well described by a two-gap γ model with gap sizes of Δ1(0)=1.31kBTc and Δ2(0)=1.80kBTc, and weak interband coupling. In contrast, ρsμSR(T), derived from the μSR data, can be fitted by a single-gap BCS model with a gap close to Δ2(0). We conclude that LaPt4Ge12 is a marginal two-gap superconductor and the small gap Δ1 seems to be suppressed by a small magnetic field applied in the μSR experiments. In comparison, the 4f electrons in PrPt4Ge12 may enhance the interband coupling and, therefore, give rise to more robust multiband superconductivity.

Source-reported materials — not catalogue approval

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