Charge-ordering cascade with spin–orbit Mott dimer states in metallic iridium ditelluride

Spin–orbit coupling results in technologically-crucial phenomena underlying magnetic devices like magnetic memories and energy-efficient motors. In heavy element materials, the strength of spin–orbit coupling becomes large to affect the overall electronic nature and induces novel states such as topological insulators and spin–orbit-integrated Mott states. Here we report an unprecedented charge-ordering cascade in IrTe2 without the loss of metallicity, which involves localized spin–orbit Mott states with diamagnetic Ir4+–Ir4+ dimers. The cascade in cooling, uncompensated in heating, consists of first order-type consecutive transitions from a pure Ir3+ phase to Ir3+–Ir4+ charge-ordered phases, which originate from Ir 5d to Te 5p charge transfer involving anionic polymeric bond breaking. Considering that the system exhibits superconductivity with suppression of the charge order by doping, analogously to cuprates, these results provide a new electronic paradigm of localized charge-ordered states interacting with itinerant electrons through large spin–orbit coupling. The influence of spin–orbit coupling on itinerant electrons underlies the formation of spin–orbit Mott states. Here, the authors demonstrate a temperature-hysteretic cascade between charge-ordered phases stabilized by localized 5dspin–orbit Mott dimer states in metallic iridium ditelluride.