Can the Mott Insulator TiOCl be Metallized by Doping? A First-Principles Study

TL;DR

This study uses first-principles calculations to explore doping effects on TiOCl, a Mott insulator, finding it remains insulating under various doping strategies and proposing potential routes to induce metallization.

Contribution

The paper provides a detailed first-principles analysis of doping effects on TiOCl and suggests possible methods to achieve metallization, which had not been conclusively demonstrated before.

Findings

TiOCl remains insulating for all studied Na doping levels

Substitutions like O by F, Cl by S, or Ti by V/Sc do not induce metallization

Proposes a doping route to potentially metallize TiOCl

Abstract

We investigate the effect of Na intercalation in the layered Mott insulator TiOCl within the framework of density functional theory. We show that the system remains always insulating for all studied Na concentrations, and the evolution of the spectral weight upon Na doping is consistent with recent photoemission experiments. We predict the Na-doped superlattice structures, and show that substitutions of O by F, Cl by S, or Ti by V (or Sc), respectively, fail to metallize the system. We propose a description in terms of a multiorbital ionic Hubbard model in a quasi-two-dimensional lattice and discuss the nature of the insulating state under doping. Finally, a likely route for metallizing TiOCl by doping is proposed.