Non-local Coulomb interactions and metal-insulator transition in Ti$_2$O$_3$: a cluster LDA+DMFT approach

TL;DR

This paper develops an ab initio cluster LDA+DMFT approach to explain the metal-insulator transition in Ti$_2$O$_3$, emphasizing the role of non-local Coulomb interactions and Ti-Ti bonding in opening a small gap.

Contribution

It introduces a cluster LDA+DMFT method that captures non-local Coulomb effects, successfully explaining the insulating phase in Ti$_2$O$_3$.

Findings

Single site DMFT fails to reproduce the insulating phase.

Non-local Coulomb interactions are crucial for the small gap.

Strong Ti-Ti bonding influences the insulating ground state.

Abstract

We present an ab initio quantum theory of the metal-insulator transition in Ti$_2$O$_3$. The recently developed cluster LDA+DMFT scheme is applied to describe the many-body features of this compound. The conventional single site DMFT cannot reproduce a low temperature insulating phase for any reasonable values of the Coulomb interaction. We show that the non-local Coulomb interactions and the strong chemical bonding within Ti-Ti pair is the origin of the small gap insulating ground state of Ti$_2$O$_3$.