69,71Ga NMR/NQR studies have been performed on a single crystal of the transuranium superconductor PuRhGa5 with Tc ≃ 9 K. We have observed a 69Ga NQR line at ≃ 29.15 MHz, and assigned it to the 4i Ga site using the NMR results. The 69Ga NQR spin-lattice relaxation rate 1/T1 shows no coherence peak just below Tc, but obeys T3 behavior below Tc. This result strongly suggests that PuRhGa5 is an unconventional superconductor having an anisotropic superconducting gap. The gap amplitude 2Δ0(T → 0) ≃ 5kBTc and the residual density of states Nres(T = 0)/N0(T = T c) ≃ 0.25 have been determined assuming a simple polar function of the form Δ(θ, φ) = A0 cos θ where θ and φ are angular parameters on the Fermi surface.
- Ga NQR