Pressure-induced Spin-Peierls to Incommensurate Charge-Density-Wave Transition in the Ground State of TiOCl

TL;DR

This study investigates how applying pressure to TiOCl causes a transition from a spin-Peierls ground state to an incommensurate charge-density-wave state, revealing a fundamental change in its electronic structure.

Contribution

It provides the first detailed structural analysis of pressure-induced phase transitions in TiOCl, highlighting the emergence of an incommensurate charge density wave.

Findings

Dimerization is suppressed near 13.1 GPa.

A new incommensurate charge density wave phase appears at high pressure.

The electronic ground state symmetry changes significantly under pressure.

Abstract

The ground state of the spin-Peierls system TiOCl was probed using synchrotron x-ray diffraction on a single-crystal sample at T = 6 K. We tracked the evolution of the structural superlattice peaks associated with the dimerized ground state as a function of pressure. The dimerization along the b axis is rapidly suppressed in the vicinity of a first-order structural phase transition at Pc = 13.1(1) GPa. The high-pressure phase is characterized by an incommensurate charge density wave perpendicular to the original spin chain direction. These results show that the electronic ground state undergoes a fundamental change in symmetry, indicating a significant change in the principal interactions.