Inelastic quasiparticle scattering andT1−1NQR relaxation rate inPr1−x

Abstract

We present an analysis of recent ͓M. Yogi et al., J. Phys. Soc. Jpn. 75, 124702 ͑2006͔͒ Sb-NQR measurements of the heavy-fermion superconductor PrOs 4 Sb 12 and the related La-doped series of superconductors Pr 1−x La x Os 4 Sb 12 . We find that this data, along with previous temperature-dependent superfluid density results and are well described by a strong-coupling order parameter containing a doping-dependent proportion of the first cubic harmonic ͑k x 4 + k y 4 + k z 4 ͒ component along with an s-wave component, when inelastic scattering due to Coulomb effects are taken into account. The resulting gap function has deep minima along the cubic axis ͓100͔, etc. but no nodes. We use the order parameter fits to generate, within the Ginzburg-Landau theory, the effective thermal mass enhancement relative to the LaOs 4 Sb 12 material and find that it rapidly varies for small x.

Field-dependent mass enhancement inPr1−xLaxOs4Sb12Zwicknagl1, Thalmeier2, Fulde3 2009Phys. Rev. BSelf Cite11180View full textAdd to dashboardCite

“…There are several reasons for that. It is a heavy fermion (γ ∼ 350 − 500mJ/molK 2 ) superconductor with a transition temperature of T c (Pr) = 1.85 K. This temperature is larger than the one of the related system LaOs 4 Sb 12 which is T c (La) = 0.74 K. A number of experiments, like those on Sb-NMR relaxation rate in Pr 1−x La x Os 4 Sb 12 [1] suggest that the superconducting order parameter is of the conventional isotropic s-wave type with possible admixture of higher harmonics depending on the Pr content [2]. However, questions and ambiguities remain.…”

Nonadiabatic effects of rattling phonons and4fexcitations inPr(Os1−xThalmeier1 2010Phys. Rev. BSelf Cite7000View full textAdd to dashboardCite

“…[2][3][4] In PrOs 4 Sb 12 and substituted compounds superconductivity appears [5][6][7] which is possibly of strongly anisotropic nature. [7][8][9] The latter has recently also been found in PrPt 4 Ge 12 . 10 It has been proposed 11,12 that low-energy crystalline electric field ͑CEF͒ excitations play an important role in the formation of Cooper pairs and likewise in the quasiparticle mass enhancement.…”

“…The symmetry of the superconducting order parameter in the skutterudites is presumably of ͑anisotropic͒ extended s-wave type. 9,11 For the present purpose we ignore the superconducting gap anisotropy. The presence of 4f states in Pr͑Os 1−x Ru x ͒ 4 Sb 12 leads to a scattering of conduction electrons from singlet-triplet CEF excitations.…”

Penetration depth study of LaOs4Sb12: Multibands-wave superconductivity

“…Sb-NQR measurement showed a coherence peak at T c and exponential temperature dependence at low temperatures. 7 The data can be fitted by an isotropic gap 7,23 with ∆(0) ≈ 1.6k B T c or an anisotropic gap ∆(θ) = δ + (∆ − δ)sinθ with ∆ = 1.73k B T c and δ = 1.21k B T c .…”