Spectroscopy of the frustrated quantum antiferromagnet Cs2CuCl4

We investigate the electronic structure of Cs2CuCl4, a material discussed in the framework of a frustrated quantum antiferromagnet, by means of resonant inelastic x ray scattering RIXS and density functional theory DFT . From the non dispersive highly localized dd excitations, we resolve the crystal field splitting of the Cu2 ions in a strongly distorted tetrahedral coordination. This allows us to model the RIXS spectrum within the crystal field theory CFT , assign the dd orbital excitations and retrieve experimentally the values of the crystal field splitting parameters Dq, Ds and Dt. The electronic structure obtained ab initio agrees with the RIXS spectrum and modelled by CFT, highlighting the potential of combined spectroscopic, cluster and DFT calculations to determine the electronic ground state of complex material