Electron molecular vibration coupling in vibrational spectra of BEDT-TTF based radical cation salts

Kozlov, Mikhail E.; Pokhodnia, K. I.; Yurchenko, A. A.

doi:10.1016/0584-8539(89)80039-x

Cited by 154 publications

(100 citation statements)

References 17 publications

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“…2 with a 16% isotope ratio, and the frequency temperature dependence shown in fig. 3 is clearly an internal mode, and is assigned to an out-of-plane bSu mode, since there are no in-plane modes with this frequency and isotope shift in the results of the normal-coordinate calculations of Kozlov et al [22]. We did not obtain an isotope shift for the feature labelled # 6 and so are unable to assign it.…”

Section: Resultsmentioning

confidence: 61%

The correlation of lattice phonon frequencies with the superconducting transition temperatures of some (BEDT-TTF) salts

Dressel

Eldridge

Williams

et al. 1992

Physica C: Superconductivity

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The far-infrared powder absorption spectra, between 10 cm-' and 350 cm-', of seven BEDT-TTF salts that exhibit superconductivity at or near ambient pressure, have been measured as a function of temperature, between 5 K and 300 K. The temperature dependences of the peak frequencies, along with the measured deuterium isotopic frequency shifts, separated the lattice from the internal modes. The frequencies of the observed lattice modes were found to increase with T, in the three K-phase salts in agreement with the reduced volume of the unit cell, and to have a mixed response in the three B-phase compounds. Furthermore, the genera1 range and magnitude of the frequencies in the higher-T, K-phase compounds were found to be larger than in the lower T, pphase compounds. Consequently, no evidence was found for a correlation between higher values of T, and a softer lattice in these organic superconductors.

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Section: Resultsmentioning

confidence: 61%

The correlation of lattice phonon frequencies with the superconducting transition temperatures of some (BEDT-TTF) salts

Dressel

Eldridge

Williams

et al. 1992

Physica C: Superconductivity

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“…50 fs indicates that the electron oscillation begins to interact coherently with the intramolecular  3 mode at the finite time delay. Considering the strong electron molecular vibration (EMV) coupling of the  3 mode [49][50][51], it is reasonable to consider that the electron oscillation selectively induces the intermolecular anti-phase  3 vibration, as shown in Figure 15f,g [49][50][51]. After 100 fs, the hollow at approximately 1450 cm -1 disappears; a broad band appears at 1450 cm -1 , reflecting the electronic dephasing [ Figure 15d and (iii) in Figure 14b].…”

Section: Ultrafast Snapshot Of Correlated Electron Dynamics 10 Fs Spementioning

confidence: 99%

“…These electron oscillations are efficiently induced between the charge-rich sites (A and B sites) and between the charge-rich site and charge-poor site (B and A' sites) [38,41,42], as shown by the arrows in Figure 16 and Figure 15f. Considering that C=C stretching modes ν 3 (presented in Figure 15g) appear between 1352 and 1476 cm -1 [49][50][51], the spectral hollow that appears at ca. 1450 cm -1 [arrow in Figure 15c and (ii) in Figure 14a,b] is attributable to the destructive interference that prevails between the electron oscillation and the intramolecular  3 mode.…”

Section: Ultrafast Snapshot Of Correlated Electron Dynamics 10 Fs Spementioning

confidence: 99%

Photoinduced Phase Transitions in α-, θ-, and κ-type ET Salts: Ultrafast Melting of the Electronic Ordering

Iwai¹

2012

Crystals

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Photoinduced phase transitions in organic compounds with strong electron correlation ET [bis(ethylenedithio)-tetrathiafulvalene)-based salts α-(ET) 2 I 3 , θ-(ET) 2 RbZn(SCN) 4 , κ-(d-ET) 2 Cu[N(CN) 2 Br] were discussed based, on time resolved optical pump-probe spectroscopy using ~150 fs mid-infrared pulse, 12 fs near infrared pulse, and sub-picosecond terahertz pulse. (i) In charge-ordered insulators α-(ET) 2 I 3 and θ-(ET) 2 RbZn(SCN) 4 , we captured ultrafast snapshots of charge dynamics i.e., immediate (ca. 15 fs) generation of a microscopic metallic state (or equivalently the microscopic melting of the charge order) which is driven by the coherent oscillation (period; 18 fs) of correlated electrons. Subsequently, condensation of the microscopic metallic state to the macroscopic scale occurs in α-(ET) 2 I 3 . However, in θ-(ET) 2 RbZn(SCN) 4 , such condensation is prevented by the large potential barrier reflecting the structural difference between the insulator and metal; (ii) In a Dimer-Mott insulator κ-(d-ET) 2 Cu[N(CN) 2 Br], photogeneration of the metallic state rises during ca. 1 ps that is much slower than the melting of charge order, because the photoinduced insulator to metal transition is driven by the intradimer molecular displacement in the dimer Mott insulator. The ultrafast dynamics of photoinduced insulator-metal transitions depend strongly on the molecular arrangement, reflecting various competing phases in the ET sheets.

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“…A normal mode analysis of BEDT-TTF 0 and BEDT-TTF 1+ was reported by Kozlov et al [42,43]. The normal modes most sensitive to the charge (valence) of the BEDT-TTF molecule are the in-phase (ν 2 , Raman active) and out-of-phase (ν 27 infrared active) stretching modes of the ring C=C bonds, and the stretching mode of the C=C bond bridging two five member rings (ν 3 , Raman active).…”

Section: Charge-sensitive Mode Of Bedt-ttfmentioning

confidence: 99%

“…The coupling constant in BEDT-TTF is estimated in refs. [43,53]. The coupling constants of ν 2 and ν 3 were respectively estimated to be g 2 = 0.043 and g 3 = 0.071 eV from an analysis of the infrared spectrum of the isolated dimer (BEDT-TTF) 2 2+ [53].…”

Section: Electron-molecular Vibration (Emv) Coupling In Bedt-ttfmentioning

confidence: 99%

Infrared and Raman Studies of Charge Ordering in Organic Conductors, BEDT-TTF Salts with Quarter-Filled Bands

Yakushi

2012

Crystals

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This paper reviews charge ordering in the organic conductors, β″-(BEDT-TTF) (TCNQ), θ-(BEDT-TTF) 2 X, and α-(BEDT-TTF) 2 X. Here, BEDT-TTF and TCNQ represent bis(ethylenedithio)tetrathiafulvalene and 7,7,8,8-tetracyanoquinodimethane, respectively. These compounds, all of which have a quarter-filled band, were evaluated using infrared and Raman spectroscopy in addition to optical conductivity measurements. It was found that β″-(BEDT-TTF)(TCNQ) changes continuously from a uniform metal to a chargeordered metal with increasing temperature. Although charge disproportionation was clearly observed, long-range charge order is not realized. Among six θ-type salts, four compounds with a narrow band show the metal-insulator transition. However, they maintain a large amplitude of charge order (Δρ~0.6) in both metallic and insulating phases. In the X = CsZn(SCN) 4 salt with intermediate bandwidth, the amplitude of charge order is very small (Δρ < 0.07) over the whole temperature range. However, fluctuation of charge order is indicated in the Raman spectrum and optical conductivity. No indication of the fluctuation of charge order is found in the wide band X = I 3 salt. In α-(BEDT-TTF) 2 I 3 the amplitude of charge order changes discontinuously from small amplitude at high temperature to large amplitude (Δρ max~0 .6) at low temperature. The long-range chargeordered state shows ferroelectric polarization with fast optical response. The fluctuation of multiple stripes occurs in the high-temperature metallic phase. Among α-(BEDT-TTF) 2 MHg(SCN) 4 (X = NH 4 , K, Rb, Tl), the fluctuation of charge order is indicated only in the X = NH 4 salt. α′-(BEDT-TTF) 2 IBr 2 shows successive phase transitions to the ferroelectric state keeping a large amplitude of charge order (Δρ max~0 .8) over the whole temperature range. It was found that the amplitude and fluctuation of charge order in these compounds is enhanced as the kinetic energy (bandwidth) decreases. OPEN ACCESSCrystals 2012, 2 1292

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Electron molecular vibration coupling in vibrational spectra of BEDT-TTF based radical cation salts

Cited by 154 publications

References 17 publications

The correlation of lattice phonon frequencies with the superconducting transition temperatures of some (BEDT-TTF) salts

The correlation of lattice phonon frequencies with the superconducting transition temperatures of some (BEDT-TTF) salts

Photoinduced Phase Transitions in α-, θ-, and κ-type ET Salts: Ultrafast Melting of the Electronic Ordering

Infrared and Raman Studies of Charge Ordering in Organic Conductors, BEDT-TTF Salts with Quarter-Filled Bands

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