Momentum-resolved single-particle spectral function for TiOCl from a combination of density functional and variational cluster calculations

TL;DR

This paper combines density functional theory and variational cluster calculations to analyze the momentum-resolved spectral function of TiOCl, revealing the importance of two-dimensional effects and interchain couplings in its electronic structure.

Contribution

It introduces a novel combined DFT and VCA approach to accurately model the spectral function of TiOCl, emphasizing the role of realistic band structure and interchain interactions.

Findings

Interchain couplings cause spectral weight redistribution in TiOCl.

Realistic 2D band structure is essential for matching ARPES data.

TiOCl exhibits strong anisotropy and 2D characteristics.

Abstract

We present results for the momentum-resolved single-particle spectral function of the low-dimensional system TiOCl in the insulating state, obtained by a combination of ab initio Density Functional Theory (DFT) and Variational Cluster (VCA) calculations. This approach allows to combine a realistic band structure and a thorough treatment of the strong correlations. We show that it is important to include a realistic two-dimensional band structure of TiOCl into the effective strongly-correlated models in order to explain the spectral weight behavior seen in angle-resolved photoemission (ARPES) experiments. In particular, we observe that the effect of the interchain couplings is a considerable redistribution of the spectral weight around the Gamma point from higher to lower binding energies as compared to a purely one-dimensional model treatment. Hence, our results support a description of TiOCl as a two-dimensional compound with strong anisotropy and also set a benchmark on the spectral features of correlated coupled-chain systems.