Temperature-induced valence and structural instability in DMTTF-CA: Single-crystal Raman and infrared measurements

Article

关键词: NEUTRAL-IONIC TRANSITION;    CHARGE-TRANSFER COMPLEXES;    QUANTUM PHASE-TRANSITION;    MIXED-STACK COMPOUNDS;    TTF-CA;    TETRATHIAFULVALENE-CHLORANIL;    PEIERLS TRANSITIONS;    P-CHLORANIL;    LATTICE;    DIMERIZATION;   

DOI  :  10.1103/PhysRevB.76.134115

来源: SCIE

【 摘 要 】

We report a detailed spectroscopic investigation of temperature-induced valence and structural instability of the mixed-stack organic charge-transfer (CT) crystal 4,4(')-dimethyltetrathiafulvalene-chloranil (DMTTF-CA). DMTTF-CA is a derivative of tetrathiafulvalene-chloranil (TTF-CA), the first CT crystal exhibiting the neutral-ionic transition by lowering temperature. We confirm that DMTTF-CA undergoes a continuous variation of the ionicity on going from room temperature down to similar to 20 K, but remains on the neutral side throughout. The stack dimerization and cell doubling, occurring at 65 K, appear to be the driving forces of the transition and of the valence instability. In a small temperature interval just below the phase transition, we detect the coexistence of molecular species with slightly different ionicities. The Peierls mode(s) precursors of the stack dimerization are identified.

【 授权许可】

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