Structural and electronic properties of α -(BEDT-TTF) 2I3 , β -(BEDT-TTF) 2I3 , and κ -(BEDT-TTF) 2X3 ( X = I, F, Br, Cl) organic charge transfer salts (original) (raw)
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Some electronic properties of the organic superconductor β - (BEDT-TTF )2I3
Journal de Physique, 1989
2014 Nous avons mesuré de 300 K à 4,2 K la magnétorésistance, la susceptibilité et l'anisotropie magnétique de monocristaux du supraconducteur organique bi-dimensionnel 03B2L-(BEDT-TTF)2I3. A partir de la magnétorésistance suivant c*, nous avons calculé une valeur de 0,5 meV pour l'intégrale de transfert tc dans un modèle de liaisons fortes. De plus, ces mesures indiquent que l'anisotropie de conductivité dans le plan a-b à basse température est d'un facteur cinq. La faible valeur du temps de relaxation (0,5 ps à 9 K) indique que le transport électronique entre plans devient incohérent, ce qui peut affecter la température de transition supraconductrice. La densité d'états dérivée de la susceptibilité de spin est en bon accord avec celle obtenue par chaleur spécifique. Lorsque le champ magnétique est dirigé perpendiculairement aux plans conducteurs, l'anisotropie magnétique provient en partie d'un diamagnétisme des électrons de conduction qui varie avec la température.
Transport properties and phase transition of organic crystal βd′ -(BEDT-TTF)2I3
Synthetic Metals, 1989
A peculiar resistivity anomaly has been observed in a new phase of (BEDT-TTF)2I 3 first synthesized recently by Zhu et al. using a diffusion method. The structure of the new phase is similar to that of its isomer ~-(BEDT-TTF)213, with a slightly different arrangement of iodine atoms and lattice constants. But, in contrast to the H-phase, which remains metallic when the temperature decreases and finally becomes a superconductor, the new phase undergoes a metal-semiconductor transition at about 140 K. Then, after a rapid rise, the resistivity peaks at ~60 K. However, the thermopower measurement shows only a small anomaly at the phase transition. A model with two energy bands is assumed to explain these phenomena. The quite different behaviour of the new phase seems to imply that the iodine anion plays a subtle role in the determination of the properties of the material.
Some electronic properties of the organic superconductor &# 946;-(BEDT-TTF) 2I3
2011
2014 Nous avons mesuré de 300 K à 4,2 K la magnétorésistance, la susceptibilité et l'anisotropie magnétique de monocristaux du supraconducteur organique bi-dimensionnel 03B2L-(BEDT-TTF)2I3. A partir de la magnétorésistance suivant c*, nous avons calculé une valeur de 0,5 meV pour l'intégrale de transfert tc dans un modèle de liaisons fortes. De plus, ces mesures indiquent que l'anisotropie de conductivité dans le plan a-b à basse température est d'un facteur cinq. La faible valeur du temps de relaxation (0,5 ps à 9 K) indique que le transport électronique entre plans devient incohérent, ce qui peut affecter la température de transition supraconductrice. La densité d'états dérivée de la susceptibilité de spin est en bon accord avec celle obtenue par chaleur spécifique. Lorsque le champ magnétique est dirigé perpendiculairement aux plans conducteurs, l'anisotropie magnétique provient en partie d'un diamagnétisme des électrons de conduction qui varie avec la température.
Lattice dynamics and electron-phonon coupling in the β-(BEDT-TTF)2I3 organic superconductor
Physical Review B, 2000
The crystal structure and lattice phonons of (BEDT-TTF)2I3 superconducting β-phase (where BEDT-TTF is bis-ethylen-dithio-tetrathiafulvalene) are computed and analyzed by the Quasi Harmonic Lattice Dynamics (QHLD) method. The empirical atom-atom potential is that successfully employed for neutral BEDT-TTF and for non superconducting α-(BEDT-TTF)2I3. Whereas the crystal structure and its temperature and pressure dependence are properly reproduced within a rigid molecule approximation, this has to be removed account for the specific heat data. Such a mixing between lattice and low-frequency intra-molecular vibrations also yields good agreement with the observed Raman and infrared frequencies. From the eigenvectors of the low-frequency phonons we calculate the electron-phonon coupling constants due to the modulation of charge transfer (hopping) integrals. The charge transfer integrals are evaluated by the extended Hückel method applied to all nearest-neighbor BEDT-TTF pairs in the ab crystal plane. From the averaged electron-phonon coupling constants and the QHLD phonon density of states we derive the Eliashberg coupling function α(ω)F (ω), which compares well with that experimentally obtained from point contact spectroscopy. The corresponding dimensionless coupling constant λ is found to be ∼ 0.4. 74.70.Kn,74.25.Kc
Electronic structure of the α-(BEDT-TTF)2I3 surface by photoelectron spectroscopy
The European Physical Journal B, 2019
We report anomalies observed in photoelectron spectroscopy measurements performed on α-(BEDT-TTF)2I3 crystals. In particular, above its metal-insulator transition temperature (T " 135 K), we observe the lack of a sharp Fermi edge in contradiction with the metallic transport properties exhibited by this quasi-bidimensional organic material. We interpret these unusual results as a signature of a one-dimensional electronic behavior confirmed by DFT band structure calculations. Using photoelectron spectroscopy we probe a Luttinger liquid with a large correlation parameter (α ą 1) that we interpret to be caused by the chain-like electronic structure of α-(BEDT-TTF)2I3 surface doped by iodine defects. These new surface effects are inaccessible by bulk sensitive measurements of electronic transport techniques.
Journal of The Physical Society of Japan, 2006
Within the framework of the density functional theory, we calculate the electronic structure of alpha\alphaalpha-(BEDT-TTF)$_2$I$_3$ at 8K and room temperature at ambient pressure and with uniaxial strain along the aaa- and bbb-axes. We confirm the existence of anisotropic Dirac cone dispersion near the chemical potential. We also extract the orthogonal tight-binding parameters to analyze physical properties. An investigation of the
NMR-analysis of electronic properties in organic superconductors (TMTSF)2PF6 and β-(BEDT-TTF)2I3
Synthetic Metals, 1987
The results of IH-NMR measurements on the single crystal of the organic superconductor (TMTSF)2PF 6 and ~-(BEDT-TTF)2I 3 are presented. A new phase transition in (TMTSF)2PF 6 was found at 4 K by IH relaxation anomaly. In 8-(BEDT-TTF)213, the IH N~ lineshape was examined at temperatures around the incommensurate structural transition. An anomalous behaviour of IH relaxation at low temperatures are discussed.
Journal of the American Chemical Society, 1986
Two new organic metals, P-(ET),ICI2 and P-(ET),BrICI, were synthesized, and their structures and electronic properties were characterized via X-ray diffraction, ESR studies, and band electronic structure calculations. BEDT-TTF, abbreviated "ET", is bis(ethylenedithio)tetrathiafulvalene, CioS8H8. The packing of the ET molecules within the sheetlike network of these two isostructural salts is significantly different from that of the two-dimensional metals /3-(ET)2X with the larger anions X-= 13-, 12Br-, 1Br2-, and Ad2-, where all but X-= 12Br-are ambient-pressure superconductors. The ESR studies for the P-(ET),ICI2 salt show that it is metallic down to-22 K, at which temperature a metal-insulator transition is observed. The band electronic structures calculated for /3-(ET)21C12 and P-(ET),BrICI reveal that these salts are one-dimensional metals. Comparison of the structures and electronic properties of the P-(ET),X salts with large linear anions (e.g., X-= 13-, 12Br-, IBr2-, and Au12-) vs. those with the small symmetric (C1-I-CI)-and asymmetric (B r-1 4-anions leads us to conclude that the nature of the interactions between ET molecules within a given sheetlike network, and hence the dimensionality of electrical properties, is strongly governed by the packing motif of ET molecules around a particular X-anion. The new synthetic metals B-(BEDT-TTF),X, where X-is a linear monovalent anion and BEDT-TTF (also known as ET) is the radical cation bis(ethy1enedithio)tetrathiafulvalene 1, have (IO) (a) Wang, H. H.
Inorganic Chemistry, 1985
A Test of Superconductivity vs. Molecular Disorder in (BEDT-'ITF)*X Synthetic Metals: Synthesis, Structure (298, 120 K), and Microwave/ESR Conductivity of (BEDT-TTF)212Br Sir: For the first time two ambient-pressure synthetic metal superconductors have been reported in a single organic radical-cation donor system, with two different symmetric trihalide anions, and based on BEDT-TTF,' abbreviated "ET". They are P-(ET),I,, with a reported superconducting transition temperature2-6 (T,) of 1.2-1.6 K, and p-(ET)21Br2, with a T, (2.3-2.8 K) t~i c e~-~ that of the 13-derivative. These two systems are isostructural with a characteristic structural motif of an extended "corrugated sheet" network of short interstack S.43 (ds...s < 3.60 A) interaction distances.e11 The S-S orbital overlap within the two-dimensional BEDT-TTF or 'ET" is bis(ethylenedithio)tetrathiafulvalene