title: Quadrupolar waves in uranium dioxide.
abstract: In presence of active orbital degrees of freedom, elementary excitations around a broken-symmetry state may include multipolar waves, but none of these exotic dispersive excitation branches has ever been identified. We show that quadrupolar waves constitute a major component of the dynamics of uranium dioxide in its magnetoquadrupolar ordered phase, and that many unexplained features in existing inelastic neutron scattering data, including a whole excitation branch, are associated with these propagating quadrupolar fluctuations. Our model permits us to separate the role of Jahn-Teller and superexchange mechanisms as sources of quadrupolar interactions.
authors.affiliation: Dipartimento di Fisica, Università di Parma, and Unità CNISM di Parma, Viale G. P. Usberti 7/A, I-43100 Parma, Italy.
authors.forename: S
authors.initials: S
authors.lastname: Carretta
authors.forename: P
authors.initials: P
authors.lastname: Santini
authors.forename: R
authors.initials: R
authors.lastname: Caciuffo
authors.forename: G
authors.initials: G
authors.lastname: Amoretti