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

• Main Author: Kenji Yonemitsu
• Format: Article
• Language: English
• Published: MDPI AG 2012-01-01
• Series: Crystals
• Subjects: photoinduced phase transition; neutral-ionic transition; charge-order melting; metal-insulator transition
• Online Access: http://www.mdpi.com/2073-4352/2/1/56
• ISSN: 2073-4352

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.