Enhanced dimerization of TiOCl under pressure: spin-Peierls - to - Peierls transition

TL;DR

This study reveals that applying high pressure to TiOCl enhances Ti3+-Ti3+ dimerization, leading to a transition from a spin-Peierls to a Peierls state, with significant electronic gap reduction.

Contribution

The paper combines experimental and computational methods to demonstrate pressure-induced dimerization enhancement and a crossover in the electronic transition mechanism in TiOCl.

Findings

Enhanced Ti3+-Ti3+ dimerization under pressure

Formation of metal-metal bonds along the b-axis

Reduction of the electronic gap and transition from spin-Peierls to Peierls state

Abstract

We report high-pressure x-ray diffraction and magnetization measurements combined with ab-initio calculations to demonstrate that the high-pressure optical and transport transitions recently reported in TiOCl, correspond in fact to an enhanced Ti3+-Ti3+ dimerization existing already at room temperature. Our results confirm the formation of a metal-metal bond between Ti3+ ions along the b-axis of TiOCl, accompanied by a strong reduction of the electronic gap. The evolution of the dimerization with pressure suggests a crossover from the spin-Peierls to a conventional Peierls situation at high pressures.