Anomalous photo-induced response by double-pulse excitation in the organic conductor (EDO-TTF)<sub>2</sub>PF<sub>6</sub>

Onda, Ken; Ogihara, Sho; Ishikawa, Tadaharu; Okimoto, Y.; Shao, Xiangfeng; Nakano, Yoshiaki; Yamochi, Hideki; Saito, Gunzi; Koshihara, Shin‐ya

doi:10.1088/1742-6596/148/1/012002

Cited by 4 publications

(3 citation statements)

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“…It is estimated that only one in 500–1500 molecules , is excited by such a pulse. How such a local event leads to a bulk phase transition is subject of speculation. ,− One possibility we see is the scenario in which a neutral bent molecule is excited to become planar. The geometry change could affect a neighbor molecule to also change geometry, thereby propagating the effect of the excitation.…”

Section: Introductionmentioning

confidence: 99%

Off-Planar Geometry and Structural Instability of EDO-TTF Explained by Using the Extended Debye Polarizability Model for Bond Angles

et al. 2012

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The geometry of ethylenedioxy-tetrathiafulvalene, EDO-TTF, plays an important role in the metal-insulator transition in the charge transfer salt (EDO-TTF)(2)PF(6). The planar and off-planar geometrical conformations of the EDO-TTF molecules are explained using an extended Debye polarizability model for the bond angle. The geometrical structure of EDO-TTF is dictated by its four sulfur bond angles and these are, in turn, determined by the polarizability of the sulfur atoms. With Hartree-Fock and second-order Møller-Plesset perturbation theory calculations on EDO-TTF, TTF, H(2)S, and their oxygen and selenium substituted counterparts we confirm this hypothesis. The Debye polarizability model for bond angles relates directly the optimum bond angle with the polarizability of the center atom. Considering the (EDO-TTF)(2)PF(6) material in this light proves to be very fruitful.

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Section: Introductionmentioning

confidence: 99%

Off-Planar Geometry and Structural Instability of EDO-TTF Explained by Using the Extended Debye Polarizability Model for Bond Angles

et al. 2012

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“…We investigated the PIPT of this complex using various ultrafast spectroscopic techniques to clarify photoinduced dynamics under strong electron-lattice and electron-electron interactions. We found unique two-step PIPT after photoexcitation of the low-temperature (0110) insulating phase [16,29,[42][43][44][45]. Note that the numbers in parentheses represent the charge order on an EDO-TTF molecule in a 1D column.…”

Section: Photoinduced Phase Transition In Strong Electron-lattice Intmentioning

confidence: 88%

Photoinduced Phase Transition in Strongly Electron-Lattice and Electron–Electron Correlated Molecular Crystals

2012

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Strongly electron-lattice-and electron-electron-correlated molecular crystals, such as charge transfer (CT) complexes, are often sensitive to external stimuli, e.g., photoexcitation, due to the cooperative or competitive correlation of various interactions present in the crystals. These crystals are thus productive targets for studying photoinduced phase transitions (PIPTs). Recent advancements in research on the PIPT of CT complexes, especially Et 2 Me 2 Sb[Pd(dmit) 2 ] 2 and (EDO-TTF) 2 PF 6 , are reviewed in this report. The former exhibits a photoinduced insulator-to-insulator phase transition with clearly assigned spectral change. We demonstrate how to find the dynamics of PIPT using this system. The latter exhibits a photoinduced hidden state as an initial PIPT process. Wide energy ranged time-resolved spectroscopy can probe many kinds of photo-absorption processes, i.e., intra-molecular and inter-molecular electron excitations and intramolecular and electron-molecular vibrations. The photoinduced spectral changes in these photo-absorption processes reveal various aspects of the dynamics of PIPT, including electronic structural changes, lattice structural changes, and molecular deformations. The complexities of the dynamics of the latter system were revealed by our measurements. OPEN ACCESSCrystals 2012, 2 1068

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“…The first step takes place within 100 fs and the photoinduced phase is assigned to the (1010) charge disproportionate phase, as shown in the lower panel of Fig. 1(a) [17][18][19][20][21][22][23][24][25][26][27][28]. The time required for the emergence of the metallic phase is 100 ps [22,23].…”

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Coherent dynamics of photoinduced phase formation in a strongly correlated organic crystal

et al. 2014

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The photoinduced phase formation in a strongly correlated crystal (EDO-TTF) 2 PF 6 (EDO-TTF: 4,5ethylenedioxytetrathiafulvalene) is investigated using a 12 fs laser pulse. The formation time is determined as 40 fs with observation of coherence of electron-phonon coupled excited states prior to formation. The temperature-independent dephasing time is determined as ß22 fs up to 180 K and the frequency of phonon oscillation is ß38 THz, corresponding to the intramolecular vibrations in EDO-TTF. The phase formation is coherently controlled by relative-phase-controlled two-pulse excitation.Strongly correlated materials exhibit intriguing phases such as superconductor, Mott insulator, spin liquid, and charge density wave [1]. Competitions between electrons, phonons, and spins in the materials play a key role in creating these phases. Photoexcitation controls this competition and initiates cooperative response resulting in a macroscopic ordering, called photoinduced phase transition (PIPT). In PIPT, electronphonon interactions lead to significant changes in dynamics. Thus, not only pure electronic but also electron-phonon dynamics have attracted considerable attention. Time-resolved optical spectroscopy has been widely used to study the electronic and vibrational dynamics and subsequent PIPT by monitoring the transient changes in optical constants on a femtosecond time scale [2][3][4][5][6]. However, the interactions dominating electronic phases are often inferred indirectly from these measurements.Coherent nonlinear spectroscopy utilizing third-order nonlinear response is a powerful tool to directly investigate interactions and has been applied to reveal ultrafast dynamics in semiconductors [7,8], light-harvesting protein complexes [9][10][11][12], and other functional materials [13,14]. However, this spectroscopy has been applied only to a few strongly correlated materials [15] because their electronic coherence is considered to be too short owing to their strong electron-electron interaction. In this Rapid Communication we have investigated 10-fs time scale dynamics of the strongly correlated organic chargetransfer (CT) complex (EDO-TTF) 2 PF 6 (EDO-TTF: 4,5ethylenedioxytetrathiafulvalene) [16], which exhibits unique PIPT due to strong electron-phonon interactions. We also revealed the formation process of the photoinduced phase * onda.k.aa@m.titech.ac.jp from the phonon-coupled excited state as well as the role of coherences in the excited state.(EDO-TTF) 2 PF 6 undergoes metal-insulator phase transition at 280 K because of its strong electron-electron and electron-phonon interactions and shows (0110)-type charge ordering below the transition temperature [16], where the number in parentheses represent the order of charge for EDO-TTF molecules, as shown in the upper panel of Fig. 1(a). This material exhibits a two-step phase transition triggered by photoexcitation in the low-temperature phase, that is, "insulator"-"photoinduced phase"-"metal" transition. The first step takes place within 100 fs and the photoinduced ph...

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Anomalous photo-induced response by double-pulse excitation in the organic conductor (EDO-TTF)₂PF₆

Cited by 4 publications

References 9 publications

Off-Planar Geometry and Structural Instability of EDO-TTF Explained by Using the Extended Debye Polarizability Model for Bond Angles

Off-Planar Geometry and Structural Instability of EDO-TTF Explained by Using the Extended Debye Polarizability Model for Bond Angles

Photoinduced Phase Transition in Strongly Electron-Lattice and Electron–Electron Correlated Molecular Crystals

Coherent dynamics of photoinduced phase formation in a strongly correlated organic crystal

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Anomalous photo-induced response by double-pulse excitation in the organic conductor (EDO-TTF)2PF6

Cited by 4 publications

References 9 publications

Off-Planar Geometry and Structural Instability of EDO-TTF Explained by Using the Extended Debye Polarizability Model for Bond Angles

Off-Planar Geometry and Structural Instability of EDO-TTF Explained by Using the Extended Debye Polarizability Model for Bond Angles

Photoinduced Phase Transition in Strongly Electron-Lattice and Electron–Electron Correlated Molecular Crystals

Coherent dynamics of photoinduced phase formation in a strongly correlated organic crystal

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Anomalous photo-induced response by double-pulse excitation in the organic conductor (EDO-TTF)₂PF₆