Revised crystal structure, disordered spin dynamics, and dichotomous magnetic excitations in a field-induced intermediate state of the honeycomb Kitaev magnet Na2Co2TeO6

초록

Na2Co2TeO6 is a primary 3d Kitaev magnet characterized by strong electronic correlations; however, its properties are not fully understood. In this study, we present a revised nuclear structure based on single-crystal neutron diffraction at ambient conditions, along with spin dynamics under magnetic fields investigated via muon spin relaxation and rotation and inelastic neutron scattering. Structural analysis resolves inconsistencies in the Na-ion ordering by revealing a triangular Na layer between the Co-based honeycomb planes. Transverse-field muon experiments confirm a quantum phase transition induced by a magnetic field at 5.7 T to a quantum-disordered state. Inelastic neutron scattering at 8.55 T applied along the a axis reveals dichotomous magnetic excitations between low-energy magnons coexisting with high-energy spinons. These findings indicate the emergence of a spin liquid-like state within a partially polarized background, highlighting the potential of this system for exploring field-induced quantum phenomena associated with Kitaev magnetism.