Incommensurate charge super-modulation and hidden dipole order in layered kitaev material α-RuCl₃

Area of Science:

• Condensed Matter Physics
• Materials Science
• Quantum Magnetism

Background:

• Kitaev materials are known for magnetism, but their charge properties and inter-degree-of-freedom coupling are less understood.
• Alpha-ruthenium trichloride (α-RuCl3) is a prominent candidate for a Kitaev quantum spin liquid, with its charge behavior needing further exploration.

Purpose of the Study:

• To investigate the charge states and their modulations in few-layered α-RuCl3 when placed in proximity to graphite.
• To explore the coupling between charge, spin, and lattice degrees of freedom in α-RuCl3 within a heterostructure.

Main Methods:

• Experimental investigation of charge states in few-layered α-RuCl3 near graphite.
• Theoretical calculations to model and reproduce observed charge phenomena.

Main Results:

• Discovery of a clear modulation of charge states in few-layered α-RuCl3, including a transition from Mott insulator to weak charge-transfer insulator.
• Observation of distinct signals of incommensurate charge and lattice super-modulations, indicating an unconventional charge order.
• Theoretical reproduction of the incommensurate charge order, attributed to the antiferroelectricity driven by internal electric fields.

Conclusions:

• There is a strong coupling between charge, spin, and lattice degrees of freedom in layered α-RuCl3 within the heterostructure.
• The findings suggest that electrical methods can be used to access and tune magnetic interactions in Kitaev compounds.