title: Direct evidence for the localized single-triplet excitations and the dispersive multitriplet excitations in SrCu2(BO3)2.
abstract: We performed inelastic neutron scattering on the 2D Shastry-Sutherland system SrCu2(11BO3)2 with an exact dimer ground state. Three energy levels at around 3, 5, and 9 meV were observed at 1.7 K. The lowest excitation at 3.0 meV is almost dispersionless with a bandwidth of 0.2 meV at most, showing a significant constraint on a single-triplet hopping owing to the orthogonality of the neighboring dimers. In contrast, the correlated two-triplet excitations at 5 meV exhibit a more dispersive behavior.
authors.affiliation: Material Design and Characterization Laboratory, Institute for Solid State Physics, University of Tokyo, Kashiwanoha, Kashiwa, Chiba 277-8581, Japan. kage@issp.u-tokyo.ac.jp
authors.forename: H
authors.initials: H
authors.lastname: Kageyama
authors.forename: M
authors.initials: M
authors.lastname: Nishi
authors.forename: N
authors.initials: N
authors.lastname: Aso
authors.forename: K
authors.initials: K
authors.lastname: Onizuka
authors.forename: T
authors.initials: T
authors.lastname: Yosihama
authors.forename: K
authors.initials: K
authors.lastname: Nukui
authors.forename: K
authors.initials: K
authors.lastname: Kodama
authors.forename: K
authors.initials: K
authors.lastname: Kakurai
authors.forename: Y
authors.initials: Y
authors.lastname: Ueda