Condensed Matter Physics, 1994, No. 3, p. 134-175, English
Title: A model with local anharmonicity in theory of HTSC systems: correlation fu nctions and "transverse" dielectric susceptibility
Authors: I.V. Stasyuk, A.M. Shvaika

The calculation of the "transverse" dielectric susceptibility of Hubb ard model including interaction with anharmonic vibrations (pseudospins) is performed using the expressions for correlation functions obtained in the generalized random phase approximation. The analysis of possible ferroelectric type anomalies is performed and the temperatures of instabilities $T^\ast$ are calculated. A phase diagram $T^\ast-n$ is plotted. The possible interpretation of the onset of superconducting phase in HTSC crystals is proposed.

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