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Theory of Photoinduced Phase Transitions in Molecular Conductors: Interplay Between Correlated Electrons, Lattice Phonons and Molecular Vibrations

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Author(s): Kenji Yonemitsu

Journal: Crystals
ISSN 2073-4352

Volume: 2;
Issue: 1;
Start page: 56;
Date: 2012;
Original page

Keywords: photoinduced phase transition | neutral-ionic transition | charge-order melting | metal-insulator transition

ABSTRACT
Dynamics of photoinduced phase transitions in molecular conductors are reviewed from the perspective of interplay between correlated electrons and phonons. (1) The charge-transfer complex TTF-CA shows a transition from a neutral paraelectric phase to an ionic ferroelectric phase. Lattice phonons promote this photoinduced transition by preparing short-range lattice dimerization as a precursor. Molecular vibrations stabilize the neutral phase so that the ionic phase, when realized, possesses a large ionicity and the Mott character; (2) The organic salts θ-(BEDT-TTF)2RbZn(SCN)4 and α-(BEDT-TTF)2I3 show transitions from a charge-ordered insulator to a metal. Lattice phonons make this photoinduced transition hard for the former salt only. Molecular vibrations interfere with intermolecular transfers of correlated electrons at an early stage; (3) The organic salt κ-(d-BEDT-TTF)2Cu[N(CN)2]Br shows a transition from a Mott insulator to a metal. Lattice phonons modulating intradimer transfer integrals enable photoexcitation-energy-dependent transition pathways through weakening of effective interaction and through introduction of carriers.

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