Lang–Firsov transformation in the generalized tight-binding method

Alexander V. Dudarev^a, Elena I. Shneyder<sup>b

a</sup> Reshetnev Siberian State University of Science and Technology, Krasnoyarsk, Russian Federation
^b Kirensky Institute of Physics,, Federal Research Center KSC SB RAS, Krasnoyarsk, Russian Federation

Abstract: The effects of strong electron-phonon interaction in a realistic model of a system with strong Coulomb correlations are analyzed using the Lang and Firsov transformation. It is shown that polaronic and bipolaronic transformations, widely discussed in the literature and associated with a smooth or sharp transitions in the properties of charge carriers when the strength of the electron-phonon coupling changes, determine the switching of the system between the regimes of correlated carriers, polarons or bipolarons. These transitions are controlled by the local electron-phonon interaction of the Holstein type. At the same time, the non local electron-lattice contribution associated with the modulation of the hopping integral plays a major role in the crossover of the polaron and bipolaron regimes in the limit of strong electron correlations.

Keywords: Lang–Firsov transformation, polaron and bipolaron crossover, pd-model.

UDC: 538.915

Received: 10.08.2023
Received in revised form: 25.09.2023
Accepted: 30.10.2023

Language: English