We report 123Sb nuclear quadrupole resonance (NQR) measurements of the filled skutterudite heavy-fermion superconductor PrOs4Sb 12 under high pressure. The temperature dependence of NQR frequency and 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. However, it is found ΔCEF and Tc stay constant above P ∼ 2 GPa revealed by Sb-NQR up to P = 3.82 GPa for the first time. Remarkably, the temperature dependence of 1/T1 below Tc = 1.55 K at P = 1.91 GPa shows no coherence peak just below Tc and power-law behavior well below Tc in contrast to the exponential decrease observed at P = 0. Present results indicate the superconductivity in PrOs4Sb 12 under pressure has nodes in the superconducting gap function.
- Nuclear quadrupole resonance
- Unconventional superconductivity
ASJC Scopus subject areas
- Physics and Astronomy(all)