Weak Interband-Coupling Superconductivity in the Filled Skutterudite LaPt4Ge12

Abstract

The superconducting pairing state of LaPt${}_4$Ge${}_{12}$ is studied by measuring the magnetic penetration depth $\lambda (T,B)$ and the superfluid density ${\rho }_s(T)$ using a tunnel-diode-oscillator (TDO)-based method and by transverse field muon-spin rotation ($\mu$SR) spectroscopy. $\lambda (T)$ follows an exponential-type temperature dependence at $T\ll T_c$, but its zero-temperature value $\lambda (0)$ increases linearly with magnetic field. Detailed analyses demonstrate that both $\lambda (T)$ and the corresponding ${\rho }_s(T)$, measured in the Meissner state by the TDO method are well described by a two-gap $\gamma$ model with gap sizes of ${\Delta }_1(0)=1.31k_B{T}_c$ and ${\Delta }_2(0)=1.80k_B{T}_c$ and a very weak interband coupling. In contrast, ${\rho }_s(T)$, derived from the $\mu \mathrm{SR}$ data taken in a small field, can be fitted by a single-gap BCS model with a gap close to ${\Delta }_2(0)$. We conclude that LaPt${}_4$Ge${}_{12}$ is a marginal two-gap superconductor and the small gap ${\Delta }_1$ seems to be destroyed by a small magnetic field. In comparison, in PrPt${}_4$Ge${}_{12}$ the $4f$-electrons may enhance the interband coupling and, therefore, give rise to more robust multiband superconductivity.

5 pages, 4 figures

References in corpus (10)

• Magnetic Penetration Depth in Unconventional Superconductors
• A review of two-band superconductivity: materials and effects on the thermodynamic and reversible mixed-state properties
• Superfluid density and specific heat within self-consistent scheme for two-band superconductor
• Superconductivity in the New Platinum Germanides MPt4Ge12 (M = Rare-earth and Alkaline-earth Metals) with Filled Skutterudite Structure
• Superconductivity in novel Ge-based skutterudites: {Sr,Ba}Pt_4Ge_{12}
• Comparison of different methods for analyzing $\mu$SR line shapes in the vortex state of type-II superconductors
• Multiband superconductivity in PrPt4Ge12 single crystals
• Broken Time Reversal Symmetry in Superconducting Pr1-xCexPt4Ge12
• On the interpretation of muon-spin-rotation experiments in the mixed state of type-II superconductors
• Superconducting parameters of BaPt(4-x)Au(x)Ge12 filled skutterudite

Cited by in corpus (6)

• Recent progress on superconductors with time-reversal symmetry breaking
• Broken Time Reversal Symmetry in Superconducting Pr1-xCexPt4Ge12
• Broken time-reversal symmetry in superconducting Pr${}_{1-x}$La${}_x$Pt${}_4$Ge${}_{12}$
• Superconducting gap structure of the skutterudite LaPt4Ge12 probed by specific heat and thermal transport
• Superconductivity in the layered cage compound Ba3Rh4Ge16
• DC-driven separation of fractional flux quanta in two-band superconductors