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.
@article{arxiv.0806.0230,
title = {Enhanced dimerization of TiOCl under pressure: spin-Peierls - to - Peierls transition},
author = {S. Blanco-Canosa and F. Rivadulla and A. Pineiro and V. Pardo and D. Baldomir and D. I. Khomskii and M. M. Abd-Elmeguid and M. A. Lopez-Quintela and J. Rivas},
journal= {arXiv preprint arXiv:0806.0230},
year = {2009}
}