Anomalous orbital structure in two-dimensional titanium dichalcogenides

TL;DR

This study investigates how trigonal lattice distortions in two-dimensional titanium dichalcogenides affect their electronic structures, revealing anomalous crystal field splitting and emphasizing the roles of hybridization and correlation.

Contribution

It provides a detailed analysis of the electronic effects of structural distortions in TiX2 compounds using spectroscopy and calculations, highlighting phenomena not explained by traditional crystal field theory.

Findings

Discovery of large, anomalous crystal field splitting in TiX2

Structural distortions significantly influence electronic properties

Metal-ligand hybridization and correlation are crucial in these materials

Abstract

Generally, lattice distortions play a key role in determining the ground states of materials. Although it is well known that trigonal distortions are generic to most two-dimensional transition metal dichalcogenides, the impact of this structural distortion on the electronic structure has not been understood conclusively. Here, by using a combination of polarization dependent X-ray absorption spectroscopy (XAS), X-ray photoelectron spectroscopy (XPS) and atomic multiplet cluster calculations, we have investigated the electronic structure of titanium dichalcogenides TiX2 (X=S, Se, Te), where the magnitude of the trigonal distortion increase monotonically from S to Se and Te. Our results reveal the presence of an anomalous and large crystal filed splitting. This unusual kind of crystal field splitting is likely responsible for the unconventional electronic structure of TiX2 compounds. Our results also indicate the drawback of the distorted crystal field picture in explaining the observed electronic ground state of these materials and emphasize the key importance of metal-ligand hybridization and electronic correlation in defining the electronic structures near Fermi energy.