Froehlich collective mode and permittivity of quasi-one-dimensional crystals with charge transfer
Buzdin A.I., Bulaevskii L.N.
It is shown that in quasi-one-dimensional complexes with charge transfer, of the TTF-TCNQ type, there exist an optically inactive Froehlich mode with a spectrum of the acoustic type and an optically active mode of phase oscillations with a gap in the spectrum; the latter mode is determined by the interaction of the charge-density waves on the neighboring cation and anion chains. An expression is obtained for the permittivity with allowance for the Froehlich mode, and estimates of the corresponding parameters are presented for TTF-TCNQ.