Anomalous orbital structure in two-dimensional titanium dichalcogenides

Area of Science:

• Condensed Matter Physics
• Materials Science
• Solid-State Chemistry

Background:

• Lattice distortions are crucial for material electronic ground states.
• Trigonal distortions are common in 2D transition metal dichalcogenides, but their precise effects on electronic structure and topology remain unclear.

Purpose of the Study:

• Investigate the electronic structure of titanium dichalcogenides (TiX2, X=S, Se, Te).
• Understand the impact of increasing trigonal distortion magnitude on electronic and topological properties.

Main Methods:

• Utilized polarization-dependent X-ray absorption spectroscopy (XAS).
• Employed X-ray photoelectron spectroscopy (XPS).
• Performed atomic multiplet cluster calculations.

Main Results:

• Observed an anomalously large crystal field splitting in TiX2 compounds.
• Found that crystal field splitting is linked to unconventional electronic structures.
• Demonstrated that distortion magnitude increases from TiS2 to TiTe2.

Conclusions:

• The large crystal field splitting, influenced by trigonal symmetry and metal-ligand hybridization, governs the electronic phase protection.
• The conventional crystal field picture is insufficient; electron-electron correlations are vital for understanding the electronic ground state at the Fermi energy.