A second-order phase transition is characterized by spontaneous symmetry breaking. The nature of the broken symmetry in the so-called "hidden order" phase transition in the heavy fermion compound URu2Si2, at transition temperature T_h=17.5 K, has posed a long-standing mystery. We report the emergence of an in-plane anisotropy of the magnetic susceptibility below T_h, which breaks the four-fold rotational symmetry of the tetragonal URu2Si2. Two-fold oscillations in the magnetic torque under in-plane field rotation were sensitively detected in small pure crystals. Our findings suggest that the hidden-order phase is an electronic "nematic" phase, a translationally invariant metallic phase with spontaneous breaking of rotational symmetry.
@article{arxiv.1107.5480,
title = {Rotational Symmetry Breaking in the Hidden-Order Phase of URu2Si2},
author = {R. Okazaki and T. Shibauchi and H. J. Shi and Y. Haga and T. D. Matsuda and E. Yamamoto and Y. Onuki and H. Ikeda and Y. Matsuda},
journal= {arXiv preprint arXiv:1107.5480},
year = {2011}
}
Comments
4 pages, 3 figures. Free reprint as published in Science online can be accessed through http://kotai2.scphys.kyoto-u.ac.jp/member/shibauchi/index.html#Science