Collective magnetic excitations in the spin ladder Sr14Cu24O41 measured using high-resolution resonant inelastic x-ray scattering

• Published in: Physical review letters Vol. 103; no. 4; p. 047401
• Main Authors: Schlappa, J, Schmitt, T, Vernay, F, Strocov, V N, Ilakovac, V, Thielemann, B, Rønnow, H M, Vanishri, S, Piazzalunga, A, Wang, X, Braicovich, L, Ghiringhelli, G, Marin, C, Mesot, J, Delley, B, Patthey, L
• Format: Journal Article
• Language: English
• Published: United States 24-07-2009
• ISSN: 0031-9007
• DOI: 10.1103/PhysRevLett.103.047401

We investigate magnetic excitations in the spin-ladder compound Sr_{14}Cu_{24}O_{41} using high-resolution Cu L_{3} edge resonant inelastic x-ray scattering (RIXS). Our findings demonstrate that RIXS couples to two-triplon collective excitations. In contrast to inelastic neutron scattering, the RIXS cross section changes only moderately over the entire Brillouin zone, revealing high sensitivity also at small momentum transfers, allowing determination of the two-triplon energy gap as 100 +/- 30 meV. Our results are backed by calculations within an effective Hubbard model for a finite-size cluster, and confirm that optical selection rules are obeyed for excitations from this spherically symmetric quantum spin-liquid ground state.