title: Spin dynamics of the 2D spin 1/2 quantum antiferromagnet copper deuteroformate tetradeuterate (CFTD).
abstract: The magnetic excitation spectrum in the two-dimensional (2D) S = 1/2 Heisenberg antiferromagnet copper deuteroformate tetradeuterate has been measured for temperatures up to T approximately J/2, where J = 6.31+/-0.02 meV is the 2D exchange coupling. For T<<J, a dispersion of the zone boundary energy is observed, which is attributed to a wave vector dependent quantum renormalization. At higher temperatures, spin-wavelike excitations persist, but are found to broaden and soften. By combining our data with numerical calculations, and with existing theoretical work, a consistent description of the behavior of the model system is found over the whole temperature interval investigated.
authors.affiliation: Condensed Matter Physics and Chemistry Department, Risø National Laboratory, DK-4000 Roskilde, Denmark.
authors.forename: H M
authors.initials: HM
authors.lastname: Rønnow
authors.forename: D F
authors.initials: DF
authors.lastname: McMorrow
authors.forename: R
authors.initials: R
authors.lastname: Coldea
authors.forename: A
authors.initials: A
authors.lastname: Harrison
authors.forename: I D
authors.initials: ID
authors.lastname: Youngson
authors.forename: T G
authors.initials: TG
authors.lastname: Perring
authors.forename: G
authors.initials: G
authors.lastname: Aeppli
authors.forename: O
authors.initials: O
authors.lastname: Syljuåsen
authors.forename: K
authors.initials: K
authors.lastname: Lefmann
authors.forename: C
authors.initials: C
authors.lastname: Rischel