Low-temperature structural effects in the (TMTSF)<mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" display="inline"><mml:msub><mml:mrow /><mml:mn>2</mml:mn></mml:msub></mml:math>PF<mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" display="inline"><mml:msub><mml:mrow /><mml:mn>6</mml:mn></mml:msub></mml:math>and AsF<mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" display="inline"><mml:msub><mml:mrow /><mml:mn>6</mml:mn></mml:msub></mml:math>Bechgaard salts

Foury-Leylekian, P.; Petit, S.; Mirebeau, I.; André, G.; Souza, M. de; Lang, Michael; Ressouche, E.; Moradpour, Alec; Pouget, Jean‐Paul

doi:10.1103/physrevb.88.024105

Cited by 16 publications

(27 citation statements)

References 50 publications

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“…This implies that the in-plane expansivities are dominated by anharmonic motions of the EtMe 3 P counterions. A dominant contribution of these isolated, weakly bound molecular units is consistent with recent results obtained on the metallic (TMTSF) 2 PF 6 salt [11]. There it was found that the thermal expansion coefficient is dominated by librational motions of the PF 6 units [11] which could be well described by Einstein oscillators.…”

Section: Resultssupporting

confidence: 89%

Lattice effects in the quasi-two-dimensional valence-bond-solid Mott insulator EtMe3P[Pd(dmit)2]2

et al. 2014

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The organic charge-transfer salt EtMe 3 P[Pd(dmit) 2 ] 2 is a quasi-two-dimensional Mott insulator with localized spins S = 1/2 residing on a distorted triangular lattice. Here we report measurements of the uniaxial thermal expansion coefficients α i along the in-plane i = a and c axis as well as along the out-of-plane b axis for temperatures 1.4 K T 200 K. Particular attention is paid to the lattice effects around the phase transition at T VBS = 25 K into a low-temperature valence-bond-solid phase and the paramagnetic regime above where effects of short-range antiferromagnetic correlations can be expected. The salient results of our study include (i) the observation of strongly anisotropic lattice distortions accompanying the formation of the valence-bond-solid phase, and (ii) a distinct anomaly in the thermal expansion coefficients in the paramagnetic regime around 40 K. Our results demonstrate that upon cooling through T VBS the in-plane c axis, along which the valence bonds form, contracts while the second in-plane a axis elongates by the same relative amount. Surprisingly, the dominant effect is observed for the out-of-plane b axis which shrinks significantly upon cooling through T VBS . The pronounced anomaly in α i around 40 K is attributed to short-range magnetic correlations. It is argued that the position of this maximum, relative to that in the magnetic susceptibility around 70 K, speaks in favor of a more anisotropic triangular-lattice scenario for this compound than previously thought.

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Section: Resultssupporting

confidence: 89%

Lattice effects in the quasi-two-dimensional valence-bond-solid Mott insulator EtMe3P[Pd(dmit)2]2

et al. 2014

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“…This observation is complemented by a recent study 48 of the thermal dependence of the lattice expansivity of (TMTSF) 2 PF 6 below 200 K, which exhibits also high temperature negative contributions 99 , and whose analysis shows that anion rotation exhibits a huge Grüneisen parameter of Γ(PF 6 ) ≈ 28. A similar value of Γ(PF 6 ) is expected in (TMTTF) 2 PF 6 because the thermal expansion coefficients have the same magnitude in (TMTSF) 2 PF 6 and (TMTTF) 2 PF 6 .…”

Section: Anomalous Lattice Properties Of the Fabre Salts In Relamentioning

confidence: 62%

“…For example, in (TMTSF) 2 ReO 4 and BF 4 the AO transition drives a MI transition stabilizing a 2k F BCDW ground state. In (TMTSF) 2 ClO 4 the kinetics of AO drives the salt to either a SDW ground state (quenched samples) or a superconducting ground state (relaxed samples), for more details see 13,27,48 .…”

Section: Non Centro-symmetric Anionsmentioning

confidence: 99%

Charge-ordering transition in (TMTTF)₂X explored via dilatometry

Souza¹,

Pouget

2013

J. Phys.: Condens. Matter

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Charge-ordering phenomena have been highly topical over the last few years. A phase transition towards a charge ordered state has been observed experimentally in several classes of materials. Among them, many studies have been devoted to the family of quasi-one dimensional organic chargetransfer salts (TMTTF)2X, where (TMTTF) stands for tetramethyltetrathiafulvalene and X for a monovalent anion (X = PF6, AsF6 and SbF6). However, the relationship between the electron localization phenomena and the role of the lattice distortion in stabilizing the charge-ordering pattern is poorly documented in the literature. Here we present a brief overview of selected literature results with emphasis placed on recent thermal expansion experiments probing the charge-ordering transition of these salts.

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“…More precisely, the thermal variation of the lattice expansion in the direction i divided by T, α i /T, or more likely the volume expansion divided by T, (Σ i α i )/T, is proportional to the entropy derivative ∂S/∂T [34]. α ┴ /T taken from the data of [24] exhibits broad maxima around 30-40 K in (TMTSF) 2 PF 6 before dropping to zero at lower temperature [34]. This finding implies that below these maxima a net decrease of the "lattice" entropy, probably due to the vanishing of the structural disorder, should occur.…”

Section: Dimerization Of the Stackmentioning

confidence: 99%

Structural Aspects of the Bechgaard and Fabre Salts: An Update

Pouget

2012

Crystals

107

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Abstract:We review structural aspects of the Bechgaard and Fabre salts in relationship with their electronic, magnetic and superconducting properties. We emphasize the role of bond and charge modulations of the quarter filled organic stack in the various instabilities and ground states exhibited by these salts. A special consideration is also devoted to the influence of anions and methyl groups in these processes. In particular we point out the importance of the anions in achieving the inter-stack coupling by either direct or indirect (via the polarization of the methyl group cavities) interactions with the donors. In this framework we discuss the role of anions and methyl group disorders in the inhibition of the divergence of the high temperature bond order wave instability of the Bechgaard salts. We analyze the modulation in the magnetic ground states by considering explicitly the coupling of the magnetization with structural degrees of freedom. We consider the role of the anions and methyl groups in stabilizing the charge ordering pattern in the Fabre salts. We also discuss the spin-Peierls transition of the Fabre salts in relation with the charge ordering transition and the adiabaticity of the phonon field. We review the anion ordering transitions by considering more particularly the influence of the ordering process on the electronic structure and on the ground states which results. In this framework we show that the texture of the anion ordered structure has direct consequences on the superconducting properties of (TMTSF) 2 ClO 4 . Finally we conclude on the essential implication of the structural degrees of freedom on the generic phase diagram of the Bechgaard and Fabre salts. OPEN ACCESSCrystals 2012, 2 467

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Low-temperature structural effects in the (TMTSF)2PF6and AsF6Bechgaard salts

Cited by 16 publications

References 50 publications

Lattice effects in the quasi-two-dimensional valence-bond-solid Mott insulator EtMe3P[Pd(dmit)2]2

Lattice effects in the quasi-two-dimensional valence-bond-solid Mott insulator EtMe3P[Pd(dmit)2]2

Charge-ordering transition in (TMTTF)₂X explored via dilatometry

Structural Aspects of the Bechgaard and Fabre Salts: An Update

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Low-temperature structural effects in the (TMTSF)2PF6and AsF6Bechgaard salts

Cited by 16 publications

References 50 publications

Lattice effects in the quasi-two-dimensional valence-bond-solid Mott insulator EtMe3P[Pd(dmit)2]2

Lattice effects in the quasi-two-dimensional valence-bond-solid Mott insulator EtMe3P[Pd(dmit)2]2

Charge-ordering transition in (TMTTF)2X explored via dilatometry

Structural Aspects of the Bechgaard and Fabre Salts: An Update

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Product

Resources

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Charge-ordering transition in (TMTTF)₂X explored via dilatometry