Odd-parity electronic multipolar ordering in URuSi; Conclusions from Si and Ru NMR measurements

Kambe, Shinsaku  ; Tokunaga, Yo  ; Sakai, Hironori   ; Hattori, Taisuke; Higa, Nonoka; Matsuda, Tatsuma*; Haga, Yoshinori   ; Walstedt, R. E.*; Harima, Hisatomo*

We report Si and Ru NMR measurements on high-quality, single-crystal URuSi samples with a residual resistivity ratio RRR70. Our results show that the Si and Ru sites exhibit 4-fold electronic symmetry around the -axis in the hidden-order state. A previously observed 2-fold contribution of Si NMR linewidth is concluded to be due to extrinsic magnetic centers. Since the U and Si sites are aligned along the -axis, we conclude further that the electronic state shows 4-fold symmetry around the U site below the hidden-order transition. From this observed local symmetry, possible space groups for the hidden-order state are or , based on group theoretical considerations. Since the order vector is considered to be , the hidden-order state is then found to be with rank 5 odd-parity, i.e. electric dotriacontapolar order.