title: Rotational symmetry breaking in the hidden-order phase of URu2Si2.
abstract: 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 URu(2)Si(2), 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 URu(2)Si(2). 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.
authors.affiliation: Department of Physics, Kyoto University, Kyoto 606-8502, Japan.
authors.forename: R
authors.initials: R
authors.lastname: Okazaki
authors.forename: T
authors.initials: T
authors.lastname: Shibauchi
authors.forename: H J
authors.initials: HJ
authors.lastname: Shi
authors.forename: Y
authors.initials: Y
authors.lastname: Haga
authors.forename: T D
authors.initials: TD
authors.lastname: Matsuda
authors.forename: E
authors.initials: E
authors.lastname: Yamamoto
authors.forename: Y
authors.initials: Y
authors.lastname: Onuki
authors.forename: H
authors.initials: H
authors.lastname: Ikeda
authors.forename: Y
authors.initials: Y
authors.lastname: Matsuda