Charge disproportionation in the metallic state of α -(BEDT-TTF)<sub>2</sub>I<sub>3</sub>

Moroto, S.; Hiraki, K.; Takano, Yoshiki; Kubo, Yasunori; Takahashi, Tohru; Yamamoto, Hiroshi; Nakamura, Tomonori

doi:10.1051/jp4:2004114096

Cited by 37 publications

(40 citation statements)

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“…The charge orderings appearing in both those two phases are the horizontal stripe, and do not exhibit any phase transitions between them. Recent theoretical estimation on charge on each site [15], based on the transfer energies obtained by the first-principles calculation [33], is consistent with both the x-ray experiment [16] and the NMR experiment [12], where the A and B sites are hole-rich and the A and C sites are electron-rich. The ZGS emerges with a further increase of P a .…”

Section: Electronic States Under Pressurementioning

confidence: 73%

“…From the nuclear magnetic resonance (NMR) experiments [10] and the angular dependence of 13 C-NMR line shape, it was confirmed that the charge stripes run along the direction perpendicular to the a-axis [11]. The charge disproportionation that exists even above T MI develops as temperature decreases from room temperature to T MI [12]. The Raman studies suggest the charge ordering in the insulating phase below T MI and also charge disproportionation above T MI [13,14].…”

Section: Introductionmentioning

confidence: 75%

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Theoretical study of the zero-gap organic conductor α-(BEDT-TTF)₂I₃

Kobayashi

Katayama

Suzumura

2009

Science and Technology of Advanced Materials

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The quasi-two-dimensional molecular conductor α-(BEDT-TTF) 2 I 3 exhibits anomalous transport phenomena where the temperature dependence of resistivity is weak but the ratio of the Hall coefficient at 10 K to that at room temperature is of the order of 10 4 . These puzzling phenomena were solved by predicting massless Dirac fermions, whose motions are described using the tilted Weyl equation with anisotropic velocity. α-(BEDT-TTF) 2 I 3 is a unique material among several materials with Dirac fermions, i.e. graphene, bismuth, and quantum wells such as HgTe, from the view-points of both the structure and electronic states described as follows. α-(BEDT-TTF) 2 I 3 has the layered structure with highly two-dimensional massless Dirac fermions. The anisotropic velocity and incommensurate momenta of the contact points, ±k 0 , originate from the inequivalency of the BEDT-TTF sites in the unit cell, where ±k 0 moves in the first Brillouin zone with increasing pressure. The massless Dirac fermions exist in the presence of the charge disproportionation and are robust against the increase in pressure. The electron densities on those inequivalent BEDT-TTF sites exhibit anomalous momentum distributions, reflecting the angular dependences of the wave functions around the contact points. Those unique electronic properties affect the spatial oscillations of the electron densities in the vicinity of an impurity. A marked behavior of the Hall coefficient, where the sign of the Hall coefficient reverses sharply but continuously at low temperatures around 5 K, is investigated by treating the interband effects of the magnetic field exactly. It is shown that such behavior is possible by assuming the existence of the extremely small amount of electron doping. The enhancement of the orbital diamagnetism is also expected. The results of the present research shed light on a new aspect of Dirac fermion physics, i.e. the emergence of unique electronic properties owing to the structure of the material.

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Section: Electronic States Under Pressurementioning

confidence: 73%

Section: Introductionmentioning

confidence: 75%

Theoretical study of the zero-gap organic conductor α-(BEDT-TTF)₂I₃

Kobayashi

Katayama

Suzumura

2009

Science and Technology of Advanced Materials

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“…Previous NMR studies on double-side substituted sample reveal that the molecular site, B, is spin-poor site in metallic phase, where, because of Knight shift, the angular dependence of the NMR shift is larger than the splitting width from Pake doublet, and the angular dependence of NMR shift shows almost a sinusoidal curve. Considering the spin disproportionation in the metallic phase is precursor phenomena of the CO transition, it is suggested that the molecular site, B, is charge-poor site in CO state [23], conflicting to the conclusion from XRD.…”

Section: Site Assignment On Charge Order Phase In α-(Bedt-ttf) 2 Imentioning

confidence: 62%

“…The NMR is an alternative tool for site assignment. From the angular dependence of NMR shift, NMR distinguishes the molecular sites in a unit cell [23]. Since NMR shift is expressed as the sum of Knight and chemical shift, NMR shift almost corresponds to the chemical shift in the spin singlet state.…”

Section: Site Assignment On Charge Order Phase In α-(Bedt-ttf) 2 Imentioning

confidence: 99%

“…Salt with another packing arrangement, α-(BEDT-TTF) 2 X and θ-(BEDT-TTF) 2 X, has been a topic of interest due to the metal-insulator (MI) transition and charge disproportionation by off-site coulomb interaction [22][23][24][25][26][27][28][29]. In this type of organic conductor, various charge disproportionation patterns are realized, and these patterns give important information about the electronic structure.…”

Section: Introductionmentioning

confidence: 99%

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Magnetic and Electric Properties of Organic Conductors Probed by 13C-NMR Using Selective-Site Substituted Molecules

2012

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Quasi-One and quasi-two dimensional organic conductors consisting of TTF derivatives such as BEDT-TTF (bis-(ethylene-dithio)-tetra-thia-fulvalene) and TMTCF (C = S; TMTTF: tetra-methyl-tetra-thia-fulvalene, C = Se; TMTSF: tetra-methyl-tetraselena-fulvalene) have been well investigated in condensed matter physics because of interest in the emerging electric and magnetic properties, such as the spin density wave, charge order, superconductivity, anti-ferromagnetism, and so on. To probe the electronic state, nuclear magnetic resonance (NMR) is one of the most powerful tools as the microscopic magnetometer. A number of 13 C-NMR studies have been performed of the double-site central 13 C= 13C bond substituted molecules. However, problems with the coupled spin system of 13 C= 13 C complicated the interpretation for observations on NMR.Therefore, single-site 13 C-enriched molecules are desired. We summarize the problem of Pake doublet and the preparation of the single-site 13 C-susbstituted BEDT-TTF and TMTCF molecules. We also demonstrate the superiority of 13 C-NMR of the single-site 13 C-susbstituted molecule utilizing the hyperfine coupling tensor.

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