title: Bond-stretching-phonon anomalies in stripe-ordered La1.69Sr0.31NiO4.
abstract: We report a neutron scattering study of bond-stretching phonons in La1.69Sr0.31NiO4, a doped antiferromagnet in which the added holes order in diagonal stripes at 45 to the Ni-O bonds. For the highest-energy longitudinal optical mode along the bonds, a softening of 20% is observed between the Brillouin zone center and the zone boundary. At 45 to the bonds, a splitting of the same magnitude is found across much of the zone. Surprisingly, the charge-ordering wave vector plays no apparent role in the anomalous dispersions. The implications for related anomalies in the cuprates are discussed.
authors.affiliation: Physics Department, Brookhaven National Laboratory, Upton, New York 11973, USA. jtran@bnl.gov
authors.forename: J M
authors.initials: JM
authors.lastname: Tranquada
authors.forename: K
authors.initials: K
authors.lastname: Nakajima
authors.forename: M
authors.initials: M
authors.lastname: Braden
authors.forename: L
authors.initials: L
authors.lastname: Pintschovius
authors.forename: R J
authors.initials: RJ
authors.lastname: McQueeney