Microscopic model for transitions from Mott to spin-Peierls insulator in TiOCl

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Zhang, Yu-Zhong
Jeschke, Harald O.
Valenti, Roser
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Abstract
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On the basis of ab initio density functional theory (DFT) calculations, we derive the underlying microscopic model Hamiltonian for TiOCl, a unique system that shows two consecutive phase transitions from a Mott insulator to a spin-Peierls insulator through a structurally incommensurate phase. We show with our model that the presence of magnetic frustration in TiOCl leads to a competition with the spin-Peierls distortion, which results in the novel incommensurate phase. In addition, our calculations indicate that the spin-Peierls state is triggered by adiabatic phonons, which is essential for understanding the nature of the phase transition.
Comment: extended version, accepted in PRB
Keywords
Condensed Matter - Strongly Correlated Electrons, Condensed Matter - Materials Science
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