Atomic-scale observation of structural and electronic orders in the layered compound α-RuCl₃

Area of Science:

• Condensed Matter Physics
• Materials Science
• Quantum Information Science

Background:

• The two-dimensional Kitaev model, hosting a quantum spin liquid ground state, is crucial for topological quantum bit development.
• Alpha-ruthenium trichloride (α-RuCl3) is a novel layered material proposed to exhibit Kitaev physics.

Purpose of the Study:

• To conduct a comprehensive, atomically resolved real-space investigation of α-RuCl3 thin films.
• To explore the material's potential for realizing Kitaev physics and its implications for quantum computing.

Main Methods:

• Scanning transmission electron microscopy (STEM) for local crystallography analysis.
• Scanning tunnelling microscopy (STM) for electronic property and charge distribution studies.

Main Results:

• Observed significant variations in ligand sublattice geometry within α-RuCl3 thin films, indicating nanoscale spatial inhomogeneity.
• Detected an electronic energy gap of approximately 0.25 eV using STM.
• Identified intra-unit cell symmetry breaking of charge distribution, with a fine structure related to charge disproportionation at Cl-terminated surfaces.

Conclusions:

• The observed geometric variations in α-RuCl3 thin films enable the realization of spatially inhomogeneous magnetic ground states.
• The findings provide critical insights into Kitaev physics in α-RuCl3, paving the way for advanced quantum materials and topological quantum bit applications.