Title: Accessing Multi-triplons in Spin Ladders using Resonant Inelastic X-ray Scattering

Abstract: Resonant inelastic x-ray scattering (RIXS) has proven a powerful tool to investigate dynamic magnetic correlations, yielding complementary insights compared to neutron scattering. A key issue is the interpretation of spectroscopic measurements in terms of quasi-particle excitations. In this paper we study the spin-conserving channel of RIXS spectra for two-leg quantum spin ladders using continuous unitary transformations. We find that multi-triplon continua and bound states are the leading contribution, opening new venues for observing and characterizing multi-triplons in quantum spin systems.