Study of the Phase Transitions of (DI-DCNQI)2M (M=Ag, Li,Cu) through the Analysis of the Temperature-Dependent Vibronic and Vibrational Infrared Absorptions

Meneghetti, Moreno; Pecile, Cesare; Yakushi, Kyuya; Yamamoto, Kaoru; Kanoda, K.; Hiraki, K.

doi:10.1006/jssc.2002.9761

Cited by 7 publications

(8 citation statements)

References 18 publications

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“… 0 for r = 1 δ j,(r+1)/2 for r odd = 1 δ j,(r+2)/2 for r even (5) Remarkably, Eq. ( 4) reproduces the same 1/r decay of spin correlations as in the usual Heisenberg chain.…”

Section: Numerical Resultsmentioning

confidence: 98%

“…Inorganic compounds, as CuGeO 3 3 or N aV 2 O 5 4 , show clear evidence in favor of the existence of spin-Peierls states with broken lattice symmetry. Even more complex phase diagrams are displayed by quasi 1D organic materials: the DI−DCN QI compounds 5,6 , the Bechgaard salts series (T M T SF ) 2 X and its sulfur analog (Fabre salts series) (T M T T F ) 2 X, where X denotes different monovalent anions (X = P F 6 , AsF 6 , ClO 4 , ...). These systems, which consist of stacks of weakly coupled chains, exhibit, at low temperature, several broken symmetry phases like charge-density-wave (CDW), spin-density-wave (SDW) and spin-Peierls (SP) before becoming superconducting 6,7 .…”

Section: Introductionmentioning

confidence: 99%

See 1 more Smart Citation

One-dimensionalt−Jmodel coupled to adiabatic phonons: A numerical investigation

Bissola

Parola

2004

Phys. Rev. B

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The ground state of the one-dimensional t-J model coupled with phonons in the adiabatic limit is numerically investigated by use of the Lanczos technique at quarter filling. Due to the interplay between the electron-electron Coulomb repulsion and electron-phonon interaction, this model shows a sequence of lattice distortions leading to the formation of charge-density-waves and bondorder-waves. Moderate electron-electron and electron-lattice coupling may lead to coexistence of dimerization and tetramerization in the distortion pattern. Dimerization leads to the formation of an "antiferromagnetic" Mott insulator, while tetramerization gives rise to a spin-Peierls phase. By increasing the super-exchange coupling, antiferromagnetism is inhibited due to the change of the distortion periodicity.

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“… 0 for r = 1 δ j,(r+1)/2 for r odd = 1 δ j,(r+2)/2 for r even (5) Remarkably, Eq. ( 4) reproduces the same 1/r decay of spin correlations as in the usual Heisenberg chain.…”

Section: Numerical Resultsmentioning

confidence: 98%

Section: Introductionmentioning

confidence: 99%

One-dimensionalt−Jmodel coupled to adiabatic phonons: A numerical investigation

Bissola

Parola

2004

Phys. Rev. B

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“…The structure of the mixed-stack CT materials is intrinsically unstable toward lattice distortion upon approaching an ionic phase with lowering temperature. , Such structural distortions are usually evidenced by intensity enhancement of the totally symmetric molecular vibrations, which are activated in the infrared spectra due to EMV coupling. , Here, we focus on the C≡N stretching TCNQF modes in the spectral range 2100–2250 cm –1 , where no EDT-TTF-I 2 vibrational modes are present. It is known that the C≡N stretching modes are charge-sensitive, so they are useful to molecular charge estimation. − As shown in our previous paper, investigations of these modes give an unambiguous evidence of the neutral-ionic phase transition.…”

Section: Resultsmentioning

confidence: 99%

“…The NIT is associated with many intriguing phenomena like a dramatic increase in electrical conductivity and dielectric constant . Among the methods used for investigations of the NIT, vibrational spectroscopy is one of the most reliable because it allows one to directly determine the charge on the donor and acceptor molecules based on its stretching modes. , The spectroscopy is also sensitive to the symmetry breaking associated with the stack distortions, which yields the intensity increasing of totally symmetric modes due to the EMV coupling. , …”

Section: Introductionmentioning

confidence: 99%

Temperature-Induced Neutral-Ionic Phase Transition in the (EDT-TTF-I₂)₂TCNQF Mixed-Stack Charge-Transfer Salt

et al. 2016

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International audienceWe report the infrared (IR) and Raman study of the 2:1 mixed-stack charge transfer salt (EDT-TTF-I2)2TCNQF, where EDT-TTF = ethylenedithiotetrathiafulvalene and TCNQ = tetracyanoquinodimethane, which undergoes a temperature-induced neutral-ionic phase transition. Polarized infrared (IR) and Raman spectra of single crystals were measured in the 8-293 K temperature range. Temperature variations of vibrational modes that are assigned to both donors and acceptors show that the average degree of charge-transfer is growing continuously from about zero at room-temperature to about 1e at T = 8 K; nevertheless, at about 100 K a regime change is observed. The coexistence of molecular species of different ionicity is detected in the whole temperature range. The IR vibrational features due to electron-molecular vibrational coupling increase their intensities considerably upon cooling giving an evidence of relatively small gradual distortions of crystal structure. Existence of ferroelectric domains is suggested. A scheme of the neutral-ionic phase transition in a 2:1 complex is proposed and discussed. © 2016 American Chemical Society

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“…The occurrence of a 4k F BOW in (DMe-DCNQI) 2 Ag and a 4k F CDW in (DI-DCNQI) 2 Ag, though not impossible, would have been rather mysterious. This mystery has very recently been resolved by Menghetti and collaborators 52 . The authors have analyzed the temperature-dependent vibronic and vibrational infrared absorptions in the (DI-DCNQI) 2 Ag system in great detail and have concluded that the low temperature phase is a 2k F bond tetramerized phase with the ...1100... CO pattern.…”

Section: A 1:2 Anionic Ctsmentioning

confidence: 99%

Pattern of charge ordering in quasi-one-dimensional organic charge-transfer solids

2003

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We examine two recently proposed models of charge ordering (CO) in the nominally 1 4 -filled, quasione-dimensional (1D) organic charge transfer solids (CTS). The two models are characterized by site charge density "cartoons" ...1010... and ...1100..., respectively. We use the Peierls-extended Hubbard model to incorporate both electron-electron (e-e) and electron-phonon (e-ph) interactions. We first compare the results, for the purely electronic Hamiltonian, of exact many-body calculations with those of Hartree-Fock (HF) mean field theory. We find that HF gives qualitatively and quantitatively incorrect values for the critical nearest-neighbor Coulomb repulsion (Vc) necessary for ...1010... order to become the ground state. Second, we establish that spin-Peierls (SP) order can occur in either the ...1100... and ...1010... states and calculate the phase diagram including both on-site and intra-site e-ph interactions. Third, we discuss the expected temperature dependence of the CO and metal-insulator (MI) transitions for both ...1010... and ...1100... CO states. Finally, we show that experimental observations clearly indicate the ...1100... CO in the 1:2 anionic CTS and the (TMTSF)2X materials, while the results for (TMTTF)2X with narrower one-electron bandwidths are more ambiguous, likely because the nearest neighbor Coulomb interaction in these materials is near Vc.

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Study of the Phase Transitions of (DI-DCNQI)2M (M=Ag, Li,Cu) through the Analysis of the Temperature-Dependent Vibronic and Vibrational Infrared Absorptions

Cited by 7 publications

References 18 publications

One-dimensionalt−Jmodel coupled to adiabatic phonons: A numerical investigation

One-dimensionalt−Jmodel coupled to adiabatic phonons: A numerical investigation

Temperature-Induced Neutral-Ionic Phase Transition in the (EDT-TTF-I₂)₂TCNQF Mixed-Stack Charge-Transfer Salt

Pattern of charge ordering in quasi-one-dimensional organic charge-transfer solids

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Study of the Phase Transitions of (DI-DCNQI)2M (M=Ag, Li,Cu) through the Analysis of the Temperature-Dependent Vibronic and Vibrational Infrared Absorptions

Cited by 7 publications

References 18 publications

One-dimensionalt−Jmodel coupled to adiabatic phonons: A numerical investigation

One-dimensionalt−Jmodel coupled to adiabatic phonons: A numerical investigation

Temperature-Induced Neutral-Ionic Phase Transition in the (EDT-TTF-I2)2TCNQF Mixed-Stack Charge-Transfer Salt

Pattern of charge ordering in quasi-one-dimensional organic charge-transfer solids

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Product

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Temperature-Induced Neutral-Ionic Phase Transition in the (EDT-TTF-I₂)₂TCNQF Mixed-Stack Charge-Transfer Salt