TiOCl, an orbital-ordered system?

TL;DR

This study uses first principles calculations to explore the electronic, magnetic, and orbital properties of TiOCl, revealing significant orbital fluctuations and proposing a microscopic explanation for its phase transition behavior.

Contribution

It provides the first detailed analysis of orbital ordering and fluctuations in TiOCl using density functional theory and phononic mode analysis.

Findings

Large orbital fluctuations driven by electron-phonon coupling

Identification of exchange pathways in TiOCl

Proposed microscopic model for phase transition behavior

Abstract

We present first principles density functional calculations and downfolding studies of the electronic and magnetic properties of the layered quantum spin system TiOCl. We discuss explicitely the nature of the exchange pathes and attempt to clarify the concept of orbital ordering in this material. An analysis of the electronic structure of slightly distorted structures according to the phononic modes allowed in this material suggests that this system is subject to large orbital fluctuations driven by the electron-phonon coupling. Based on these results, we propose a microscopic explanation of the behavior of TiOCl near the phase transition to a spin-gapped system.