Evidence for Lattice Effects at the Charge-Ordering Transition in (TMTTF)${}_2$X

Abstract

High-resolution thermal expansion measurements have been performed for exploring the mysterious "structureless transition" in (TMTTF)${}_2$X (X = PF${}_6$ and AsF${}_6$), where charge ordering at $T_{CO}$ coincides with the onset of ferroelectric order. Particularly distinct lattice effects are found at $T_{CO}$ in the uniaxial expansivity along the interstack $\text{c*}$-direction. We propose a scheme involving a charge modulation along the TMTTF stacks and its coupling to displacements of the counteranions X${}^{-}$. These anion shifts, which lift the inversion symmetry enabling ferroelectric order to develop, determine the 3D charge pattern without ambiguity. Evidence is found for another anomaly for both materials at $T_{int}$ $\simeq$ 0.6 $\cdot$ $T_{CO}$ indicative of a phase transition related to the charge ordering.

References in corpus (9)

• Charge ordering in the TMTTF family of molecular conductors
• The ferroelectric Mott-Hubbard phase of organic (TMTTF)2X conductors
• Antiferromagnetic Phases of One-Dimensional Quarter-Filled Organic Conductors
• Theoretical Aspects of Charge Ordering in Molecular Conductors
• Dielectric response of charge induced correlated state in the quasi-one-dimensional conductor (TMTTF)2PF6
• Electron-lattice coupling and the broken symmetries of the molecular salt (TMTTF)${}_2$SbF${}_6$
• Anomalous Lattice Response at the Mott Transition in a Quasi-2D Organic Conductor
• Influence of the anion potential on the charge ordering in quasi-one dimensional charge transfer salts
• Effects of Two Energy Scales in Weakly Dimerized Antiferromagnetic Quantum Spin Chains

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• Evidence for electronically-driven ferroelectricity in the family of strongly correlated dimerized BEDT-TTF molecular conductors
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• Exploring the Charge-Ordering Transition in (TMTTF)${}_2$X via Thermal Expansion Measurements
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• Microwave dielectric study of spin-Peierls and charge ordering transitions in (TMTTF)${}_2$PF${}_6$ salts
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• Charge Order Breaks Magnetic Symmetry in Molecular Quantum Spin Chains
• Probing the Ionic Dielectric Constant Contribution in the Ferroelectric Phase of the Fabre-Salts
• Magneto-elastic coupling in the spin-Peierls ground state of hydrogenated and deuterated (TMTTF)${}_2$PF${}_6$ salts
• Electron spins interaction in the spin-Peierls phase of the organic spin chain (o -DMTTF) 2 X (X = Cl, Br, I)
• Superlattice Induced by Charge Order in the Organic Spin Chain (TMTTF)${}_{2}X$ ($X=$ SbF${}_6$, AsF${}_6$ and PF${}_6$) Revealed by High Field EPR
• Charge-order phase transition in the quasi one-dimensional organic conductor (TMTTF)${}_2$NO${}_3$
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• Combined experimental and theoretical studies on glasslike transitions in the frustrated molecular conductors $\theta$-(BEDT-TTF)${}_{2}M{M}^{\prime }$(SCN)${}_4$
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