title: One- and two-triplon spectra of a cuprate ladder.
abstract: We have performed inelastic neutron scattering on the near ideal spin-ladder compound La4Sr10Cu24O41 as a starting point for investigating doped ladders and their tendency toward superconductivity. A key feature was the separation of one-triplon and two-triplon scattering. Two-triplon scattering is observed quantitatively for the first time and so access is realized to the important strong magnetic quantum fluctuations. The spin gap is found to be 26.4+/-0.3 meV. The data are successfully modeled using the continuous unitary transformation method, and the exchange constants are determined by fitting to be Jleg=186 meV and Jrung=124 meV along the leg and rung, respectively; a substantial cyclic exchange of Jcyc=31 meV is confirmed.
authors.affiliation: Hahn-Meitner-Institut Berlin, Berlin, Germany.
authors.forename: S
authors.initials: S
authors.lastname: Notbohm
authors.forename: P
authors.initials: P
authors.lastname: Ribeiro
authors.forename: B
authors.initials: B
authors.lastname: Lake
authors.forename: D A
authors.initials: DA
authors.lastname: Tennant
authors.forename: K P
authors.initials: KP
authors.lastname: Schmidt
authors.forename: G S
authors.initials: GS
authors.lastname: Uhrig
authors.forename: C
authors.initials: C
authors.lastname: Hess
authors.forename: R
authors.initials: R
authors.lastname: Klingeler
authors.forename: G
authors.initials: G
authors.lastname: Behr
authors.forename: B
authors.initials: B
authors.lastname: Büchner
authors.forename: M
authors.initials: M
authors.lastname: Reehuis
authors.forename: R I
authors.initials: RI
authors.lastname: Bewley
authors.forename: C D
authors.initials: CD
authors.lastname: Frost
authors.forename: P
authors.initials: P
authors.lastname: Manuel
authors.forename: R S
authors.initials: RS
authors.lastname: Eccleston