Rapid Communication Abstract: A broad low-frequency Raman band is observed in the proximity of the temperature-induced neutral-ionic phase transition (NIT) of a mixed-stack charge-transfer crystal, 4,4'-dimethyltetrathiafulvalene-chloranil (DMTTF-CA). Adopting a modified Hubbard model with coupling to lattice phonons and molecular vibrations, we propose a time-correlation-function approach to the calculation of the Raman and infrared spectra of these quasi-one-dimensional systems. The approach provides a unifying picture for several puzzling features observed in vibrational spectra across the NIT, and ascribes the anomalous intensity of the Raman band to the divergent polarizability of the electronic system.
Correlated electrons in soft lattices: Raman scattering evidence of the nonequilibrium dielectric divergence at the neutral-ionic phase transition / G. D’Avino; M. Masino; A. Girlando; A. Painelli. - In: PHYSICAL REVIEW. B, CONDENSED MATTER AND MATERIALS PHYSICS. - ISSN 1098-0121. - 83(2011), p. 161105. [10.1103/PhysRevB.83.161105]
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