Pressure-induced spin-Peierls to incommensurate charge-density-wave transition in the ground state of TiOCl

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 P[subscript C]=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.