EXISTENCE OF LINE-NODES IN THE SUPERCONDUCTING ENERGY-GAP OF ANTIFERROMAGNETIC SUPERCONDUCTOR URU2SI2-RU-101 NQR STUDY

We have carried out Ru-101 NQR measurements of URu2Si2 in zero magneti c field in the temperature, T, range from 0.16 K to 26 K. From the NQR spectrum, the electric quadrupole interaction parameters were determi ned to be nu(Q) =5.72 MHz and eta =0. The nuclear spin-lattice relaxat ion rate, 1/T-1, decreases drastically below 17.5 K. This decrease is associated with antiferromagnetic ordering. In the superconducting sta te, 1/T-1 has no coherence peak just below T-c=1.2 K, and decreases in proportion to T-3 With no deviation down to 0.2 K, which indicates th e existence of line nodes in the superconducting energy gap.