Anisotropic Superconducting Gap in Transuranium Superconductor PuRhGa₅: Ga NQR Study on a Single Crystal

Abstract

^{69,71}Ga NMR/NQR studies have been performed on a single crystal of the\ntransuranium superconductor PuRhGa_{5} with Tc ~ 9 K. We have observed a\n^{69}Ga NQR line at ~29.15 MHz, and assigned it to the $4i$ Ga site using the\nNMR results. The ^{69}Ga NQR spin-lattice relaxation rate 1/T_{1} shows no\ncoherence peak just below Tc, but obeys a T^{3} behavior below Tc. This result\nstrongly suggests that PuRhGa_{5} is an unconventional superconductor having an\nanisotropic superconducting gap.\n