Sb-NQR probe for superconducting property in the Pr-based filled skutterudite compound PrRu4Sb12

Abstract

We report the electronic and superconducting properties in the Pr-based filled-skutterudite superconductor PrRu${}_4$Sb${}_{12}$ with $T_c=1.3$ K via the measurements of nuclear-quadrupole-resonance (NQR) frequency ${\nu }_Q$ and nuclear-spin-lattice-relaxation time $T_1$ of Sb nuclei. The temperature dependence of ${\nu }_Q$ has revealed the energy scheme of Pr${}^{3+}$ crystal electric field (CEF) that is consistent with an energy separation ${\Delta }_{CEF}\sim 70$K between the ground state and the first-excited state. In the normal state, the Korringa relation of $(1/T_{1}T{)}_{Pr}$=const. is valid, with [$(1/T_{1}T$)${}_{Pr}$/$(1/T_{1}T$)${}_{La}$]${}^{1/2}$ $\sim$ 1.44 where $(1/T_{1}T{)}_{La}$ is for LaRu${}_4$Sb${}_{12}$. These results are understood in terms of a conventional Fermi liquid picture in which the Pr-$4f^2$ state derives neither magnetic nor quadrupolar degrees of freedom at low temperatures. In the superconducting state, $1/T_1$ shows a distinct coherence peak just below $T_c$, followed by an exponential decrease with a value of 2$\Delta /k_B{T}_c$ = 3.1. These results demonstrate that PrRu${}_4$Sb${}_{12}$ is a typical weak-coupling s-wave superconductor, in strong contrast with the heavy-fermion superconductor PrOs${}_4$Sb${}_{12}$ that is in an unconventional strong coupling regime. The present study on PrRu${}_4$Sb${}_{12}$ highlights that the Pr-$4f^2$derived non-magnetic doublet plays a key role in the unconventional electronic and superconducting properties in PrOs${}_4$Sb${}_{12}$.

4 page with 3 figures embedded in the text. Submitted in Phys. Rev. B

References in corpus (3)

• Thermodynamical Study on the Heavy-Fermion Superconductor PrOs4Sb12: Evidence for Field-Induced Phase Transition
• Evidence for Unconventional Strong-coupling Superconductivity in PrOs_4Sb_12 : An Sb Nuclear Quadrupole Resonance (NQR) Study
• Fermi surface of the heavy fermion superconductor PrOs${}_4$Sb${}_{12}$

Cited by in corpus (14)

• Recent progress on superconductors with time-reversal symmetry breaking
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• Evolution of crystalline electric field effects, superconductivity, and heavy fermion behavior in the specific heat of Pr(Os${}_{1-x}$Ru${}_x$)${}_4$Sb${}_{12}$
• Probing the superconducting gap symmetry of PrRu${}_4$Sb${}_{12}$: A comparison with PrOs${}_4$Sb${}_{12}$
• Superconducting properties of Pr-based Filled skutterudite PrRu${}_4$As${}_{12}$
• Microscopic Approach to Magnetism and Superconductivity of $f$-Electron Systems with Filled Skutterudite Structure
• Exciton Mediated Superconductivity in PrOs4Sb12
• Evolution of superconducting order in Pr(Os${}_{1-x}$Ru${}_x$)${}_4$Sb${}_{12}$
• Magnetic Fluctuations of Filled Skutterudites Emerging in the Transition Region between Singlet and Triplet States
• Exciton Mediated Triplet Superconductivity in Th System PrOs4Sb12
• 123Sb-NQR study of unconventional superconductivity in the filled skutterudite heavy-fermion compound PrOs4Sb12 under high pressure up to P = 3.82 GPa
• Inelastic neutron scattering studies of Crystal Field Levels in PrOs${}_4$As${}_{12}$
• Effect of Impurities Scattering Potential on NMR relaxation rate in impure d-wave superconductors