We report 123Sb nuclear quadrupole resonance (NQR) measurements of the filled skutterudite heavyfermion superconductor PrOs4Sb 12 under high pressures of 1.91 and 2.34 GPa. The temperature dependence of NQR frequency and the spin-lattice relaxation rate 1/T1 indicate that the crystal-electric-field splitting ΔCEF between the ground state Γ1 singlet and the first excited state Γ4(2) triplet decreases with increasing pressure. The 1/T1 below Tc = 1.55 K at P = 1:91 GPa shows a power-law temperature variation and is proportional to T5 at temperatures considerably below Tc, which indicates the existence of point nodes in the superconducting gap function. The data can be well fitted by the gap model Δ(θ) = Δ0 sinθ with Δ0 = 3.08kBTc. The relation between the superconductivity and the quadrupole fluctuations associated with the Γ4(2) state is discussed.
ASJC Scopus subject areas
- Physics and Astronomy(all)