Zoran Ivić

Radiative decay of the one-dimensional large acoustic polaron

Abstract Finite temperature dynamics and stability of the adiabatic large acoustic polaron in one-dimensional systems have been examined by means of the perturbation method based upon the inverse scattering transform. Polaron life-time was estimated in dependence of temperature and electron (exciton)–phonon coupling constant.

Properties of the moving Holstein large polaron in one-dimensional molecular crystals.

The features of the moving large polaron are investigated within Holsteins molecular crystal model. The necessity to account for the phonon dispersion is emphasized and its impact on polaron properties is examined in detail. It was found that the large polaron dynamics is described by the nonlocal nonlinear Schrödinger equation. The character of its solutions is determined by the degree of nonlocality, which is specified by the polaron velocity and group velocity of the lattice modes. An analytic solution for the polaron wavefunction is obtained in the weakly nonlocal limit. It was found that the polaron velocity and phonon dispersion have a significant impact on the parameters and dynamics of large polarons. The polaron amplitude and effective mass increase while its spatial extent decreases with a rise in the degree of nonlocality. The criterion for the stability of large polaron is formulated in terms of the values of the degree of nonlocality, the magnitude of the basic energy parameters of the system and the polaron velocity. It turns out that the large polaron velocity cannot exceed a relatively small limiting value. A similar limitation on large polaron velocity has not been found in previous studies. The consequences of these results on polaron dynamics in realistic conditions are discussed.

Polaron induced modification of the speed of sound in quasi-one-dimensional molecular crystals

Abstract We study the possible influence of polaron effect on the phonon spectrum in quasi-one-dimensional molecular chains. It was found that polaron induced phonon correlations may lead to the characteristic modifications of the phonon frequencies and speed of sound which shows specific temperature dependence for particular type of polaron.

Localization versus delocalization in simple two-state models: variational estimates

Abstract We study a two-level system coupled to the set of harmonic oscillators by application of a simple variational approach whose equations can in principle be solved in the whole range of system parameters. The conditions for localization are studied for the molecular crystal model and the acoustic deformation potential model.

Adiabatic large polarons in anisotropic molecular crystals

Adiabatic large polarons in anisotropic molecular crystals We study the large polaron whose motion is confined to a single chain in a system composed of the collection of parallel molecular chains embedded in threedimensional lattice. It is found that the interchain coupling has a significant impact on the large polaron characteristics. In particular, its radius is quite larger while its effective mass is considerably lighter than that estimated within the one-dimensional models. We believe that our findings should be taken into account for the proper understanding of the possible role of large polarons in the charge and energy transfer in quasi-one-dimensional substances.

Inapplicability of Small-Polaron Model for the Explanation of Infrared Absorption Spectrum in Acetanilide

The applicability of small-polaron model for the interpretation of infrared absorption spectrum in acetanilide has been critically reexamined. It is shown that the energy difference between the normal and anomalous peak, calculated by means of small-polaron theory, displays pronounced temperature dependence which is in drastic contradiction with experiment. It is demonstrated that self-trapped states, which are recently suggested to explain theoretically the experimental absorption spectrum in protein, cannot cause the appearance of the peaks in absorption spectrum for acetanilide.