paper

Collective spin excitations in a quantum spin ladder probed by high-resolution Resonant Inelastic X-ray Scattering

arXiv:0901.1331 · doi:10.1103/PhysRevLett.103.047401

Abstract

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 collective spin excitations from a quantum spin-liquid ground state. In contrast to Inelastic Neutron Scattering (INS), the RIXS cross section changes only moderately over the entire Brillouin Zone (BZ), revealing a high sensitivity also at small momentum transfers. The two-triplon energy gap is found to be $100 \pm 30$ meV. Our results are supported by calculations within an effective Hubbard model for a finite-size cluster.

10 pages, 4 figures, revised version