Two pressure-induced transitions in TiOCl: Mott insulator to anisotropic metal

Abstract

Using Car-Parrinello molecular dynamics calculations we investigate the behavior of the low-dimensional multiorbital Mott insulator TiOCl under pressure. We show that the system undergoes {\it two} consecutive phase transitions, first at $P_{\text{c}}$ from a Mott-insulator to a metallic phase in the $ab$ plane with a strong Ti-Ti dimerization along $b$. At a pressure $P_{\text{c}}^{\prime }>P_{\text{c}}$ the dimerization disappears and the system behaves as a uniform metal. This second transition has not yet been reported experimentally. We show that the insulator-to-metal transition at $P_{\text{c}}$ is driven by the widening of the bandwidth rather than structural changes or reduction of crystal field splittings and it shows a redistribution of the electronic occupation within the $t_{2g}$ bands. Our computed pressure-dependent lattice parameters are consistent with experimental observations and the existing controversy on the change of crystal symmetry at high pressures is discussed.

arXiv comment4 pages, 4 figures, accepted in PRL

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• Determination of effective microscopic models for the frustrated antiferromagnets Cs${}_2$CuCl${}_4$ and Cs${}_2$CuBr${}_4$ by density functional methods
• Proximity of LaOFeAs to a magnetic instability
• Microscopic model for transitions from Mott to spin-Peierls insulator in TiOCl
• Can the Mott Insulator TiOCl be Metallized by Doping? A First-Principles Study
• Momentum-resolved single-particle spectral function for TiOCl from a combination of density functional and variational cluster calculations
• Orbital Selective Phase Transition
• Two pressure-induced structural phase transitions in TiOCl
• Pressure-driven phase transitions in correlated systems
• Heat conductivity of the spin-Peierls compounds TiOCl and TiOBr
• Pressure-induced Spin-Peierls to Incommensurate Charge-Density-Wave Transition in the Ground State of TiOCl