title: Direct bulk-sensitive probe of 5f symmetry in URu2Si2.
abstract: The second-order phase transition into a hidden order phase in URu2Si2goes along with an order parameter that is still a mystery, despite 30 years of research. However, it is understood that the symmetry of the order parameter must be related to the symmetry of the low-lying local electronic [Formula: see text]-states. Here, we present results of a spectroscopic technique, namely core-level nonresonant inelastic X-ray scattering (NIXS). This method allows for the measurement of local high-multipole excitations and is bulk-sensitive. The observed anisotropy of the scattering function unambiguously shows that the 5[Formula: see text] ground-state wave function is composed mainly of the [Formula: see text] with majority [Formula: see text] = [Formula: see text] + [Formula: see text] and/or [Formula: see text] singlet states. The incomplete dichroism indicates the possibility that quantum states of other irreducible representation are mixed into the ground state.
authors.affiliation: Institute of Physics II, University of Cologne, 50937 Cologne, Germany.
authors.forename: Martin
authors.initials: M
authors.lastname: Sundermann
authors.affiliation: Max-Planck-Institute for Chemical Physics of Solids, 01187 Dresden, Germany.
authors.forename: Maurits W
authors.initials: MW
authors.lastname: Haverkort
authors.affiliation: Max-Planck-Institute for Chemical Physics of Solids, 01187 Dresden, Germany.
authors.forename: Stefano
authors.initials: S
authors.lastname: Agrestini
authors.affiliation: European Synchrotron Radiation Facility, 38043 Grenoble Cédex, France.
authors.forename: Ali
authors.initials: A
authors.lastname: Al-Zein
authors.affiliation: European Synchrotron Radiation Facility, 38043 Grenoble Cédex, France.
authors.forename: Marco
authors.initials: M
authors.lastname: Moretti Sala
authors.affiliation: Van der Waals-Zeeman Institute, University of Amsterdam, 1098 XH Amsterdam, The Netherlands.
authors.forename: Yingkai
authors.initials: Y
authors.lastname: Huang
authors.affiliation: Van der Waals-Zeeman Institute, University of Amsterdam, 1098 XH Amsterdam, The Netherlands.
authors.forename: Mark
authors.initials: M
authors.lastname: Golden
authors.affiliation: Van der Waals-Zeeman Institute, University of Amsterdam, 1098 XH Amsterdam, The Netherlands.
authors.forename: Anne
authors.initials: A
authors.lastname: de Visser
authors.affiliation: Max-Planck-Institute for Chemical Physics of Solids, 01187 Dresden, Germany.
authors.forename: Peter
authors.initials: P
authors.lastname: Thalmeier
authors.affiliation: Max-Planck-Institute for Chemical Physics of Solids, 01187 Dresden, Germany.
authors.forename: Liu Hao
authors.initials: LH
authors.lastname: Tjeng
authors.affiliation: Institute of Physics II, University of Cologne, 50937 Cologne, Germany; severing@ph2.uni-koeln.de.
authors.forename: Andrea
authors.initials: A
authors.lastname: Severing
keywords: X-ray spectroscopy; crystal-electric field; heavy fermions; hidden order; strongly correlated electron systems