We report the electronic and superconducting properties in the Pr-based filled-skutterudite superconductor PrRu4Sb12 with Tc = 1.3 K via the measurements of nuclear-quadrupole-resonance frequency νQ and nuclear-spin-lattice-relaxation time T1 of Sb nuclei. The temperature dependence of νQ has revealed the energy scheme of Pr3+ crystal electric field that is consistent with an energy separation ΔCEF 70 K between the ground state and the first-excited state. In the normal state, the Korringa relation of (1/T1T)Pr = const is valid, with [(1/T1T)Pr/(1/T1T)La]1/2 1.44, where (1/T1T)La is for LaRu4Sb12. These results are understood in terms of a conventional Fermi-liquid picture in which the Pr-4f2 state derives neither magnetic nor quadrupolar degrees of freedom at low temperatures. In the superconducting state, 1/T1 shows a distinct coherence peak just below Tc, followed by an exponential decrease with a value of 2Δ/kBTc = 3.1. These results demonstrate that PrRu4Sb12 is a typical weak-coupling s-wave superconductor, in strong contrast with the heavy-fermion superconductor PrOs4Sb12 that is in an unconventional strong coupling regime. The present study on PrRu4Sb12 highlights that the Pr-4f2-derived nonmagnetic doublet plays a key role in the unconventional electronic and superconducting properties in PrOs4Sb12.
|Journal||Physical Review B - Condensed Matter and Materials Physics|
|Publication status||Published - May 9 2003|
ASJC Scopus subject areas
- Electronic, Optical and Magnetic Materials
- Condensed Matter Physics