Probing Magnetic excitation and Crystal Field States in the Quasi-2D Honeycomb layered oxide Na3Cu2SbO6

The quasi-2D honeycomb material Na3Cu2SbO6, featuring spin-1/2 Cu ions, presents a compelling platform to study the interplay between geometric (Crystal field), anisotropic exchange, and moderate to strong spin-orbit coupling. Our macroscopic characterization of polycrystalline Na3Cu2SbO6
reveals a broad peak in DC magnetization data around 90 K, and a curious upturn at low temperatures. The material adopts a monoclinic C2/m crystal structure where a significant Jahn-Teller (JT) distortion of the CuO6 octahedra is evident. This distortion is expected to induce both anisotropic
magnetic exchange and a splitting of the Cu2+ crystal field ground state. We propose to use high-flux inelastic neutron scattering on the MERLIN spectrometer to perform the low-energy excitation spectrum of Na3Cu2SbO6. These measurements will allow us to map the collective magnetic
excitations to quantify the spin structure and, simultaneously, to search for the localized crystal field excitation to experimentally measure the JT splitting energy. This experiment will provide a complete microscopic picture of the electronic and magnetic interactions governing this intriguing quantum material.