title: Determining the in-plane orientation of the ground-state orbital of CeCu2Si2.
abstract: We have successfully determined the hitherto unknown sign of the B(4)(4) Stevens crystal-field parameter of the tetragonal heavy-fermion compound CeCu(2)Si(2) using vector q-dependent nonresonant inelastic x-ray scattering experiments at the cerium N(4,5) edge. The observed difference between the two different directions, q∥[100] and q∥[110], is due to the anisotropy of the crystal-field ground state in the (001) plane and is observable only because of the utilization of higher than dipole transitions possible in nonresonant inelastic x-ray scattering. This approach allows us to go beyond the specific limitations of dc magnetic susceptibility, inelastic neutron scattering, and soft x-ray spectroscopy, and provides us with a reliable information about the orbital state of the 4f electrons relevant for the quantitative modeling of the quasiparticles and their interactions in heavy-fermion systems.
authors.affiliation: Institute of Physics II, University of Cologne, Zülpicher Straße 77, D-50937 Cologne, Germany.
authors.forename: T
authors.initials: T
authors.lastname: Willers
authors.forename: F
authors.initials: F
authors.lastname: Strigari
authors.forename: N
authors.initials: N
authors.lastname: Hiraoka
authors.forename: Y Q
authors.initials: YQ
authors.lastname: Cai
authors.forename: M W
authors.initials: MW
authors.lastname: Haverkort
authors.forename: K-D
authors.initials: KD
authors.lastname: Tsuei
authors.forename: Y F
authors.initials: YF
authors.lastname: Liao
authors.forename: S
authors.initials: S
authors.lastname: Seiro
authors.forename: C
authors.initials: C
authors.lastname: Geibel
authors.forename: F
authors.initials: F
authors.lastname: Steglich
authors.forename: L H
authors.initials: LH
authors.lastname: Tjeng
authors.forename: A
authors.initials: A
authors.lastname: Severing