Dependence of the nature of the Holstein polaron motion in a polynucleotide chain subjected to a constant electric field on the initial polaron state and the parameters of the chain

In this work, we consider the motion of a polaron in a polynucleotide Holstein molecular chain in a constant electric field. It is shown that the character of the polaron motion in the chain depends not only on the chosen parameters of the chain, but also on the initial distribution of the charge along the chain. It is shown that for a small set value of the electric field intensity and for fixed values of the chain parameters, changing only the initial distribution of the charge in the chain, it is possible to observe either a uniform movement of the charge along the chain, or an oscillatory mode of charge movement.

Zero temperature momentum distribution of an impurity in a polaron state of one-dimensional Fermi and Tonks-Girardeau gases

We investigate the momentum distribution function of a single distinguishable impurity particle which formed a polaron state in a gas of either free fermions or Tonks-Girardeau bosons in one spatial dimension. We obtain a Fredholm determinant representation of the distribution function for the Bethe ansatz solvable model of an impurity-gas \deltaδ-function interaction potential at zero temperature, in both repulsive and attractive regimes. We deduce from this representation the fourth power decay at a large momentum, and a weakly divergent (quasi-condensate) peak at a finite momentum. We also demonstrate that the momentum distribution function in the limiting case of infinitely strong interaction can be expressed through a correlation function of the one-dimensional impenetrable anyons.

The Peculiarities of Charge Motion in the Molecular Polynucleotide Chains of Finite Length. The Rapid Formation of a Moving Polaron State

The numerical experiments which demonstrate the possibility of charge transfer in a homogeneous G/C DNA chain in the absence of an electric field have been carried out. As a model, which describes the dynamics of a DNA molecule, was considered the nonlinear Peyrard-Bishop-Dauxois-Holstein model. It is commonly supposed that the main electric current carrier in homogeneous synthetic polynucleotide chains is the polaron. We have previously studied the peculiarities of polaron motion in molecular polynucleotide chains of finite length. It was shown that a polaron placed at the initial moment of time not in the center of the chain acquires the ability to move in the absence of an electric field and in the absence of any additional excitations in the chain. The numerical experiments which demonstrate the possibility of polaron charge transfer in a homogeneous finite unclosed G/C DNA chain due to the interaction with localized excitations have been carried out in the absence of an electric field. In this study, at the initial moment of time, a polaron is not added to the chain, but a charge localized in the region of a certain number of neighboring sites displaced from the equilibrium positions. The motion of the charge in the chain is caused by choice of these specified initial conditions, which ensure the rapid formation of the polaron state and, as a consequence, charge transfer along the chain. For the assignment of the external nonlinear excitations, we used nonzero values of the displacements of particles and/or their velocities at the initial instant of time. Non-zero values of chain sites velocities at the initial time were used to stimulate the motion of the charge. It is shown that for the rapid formation of the polaron state, the initial conditions must correspond to the parameters of the polaron, which is formed in the chain under the chosen parameters. It is shown that, depending on the parameters of the chain and on the parameters of the selected initial conditions, the charge can be transferred along the chain over long distances.

Спиновая физика экситонов в коллоидных нанокристаллах

We present a review of spin-dependent properties of excitons in semiconductor colloidal nanocrystals. The photoluminescences (PL) properties of neutral and charged excitons (trions) are compared. The mechanisms and the polarization of radiative recombination of a “dark” (spin-forbidden) exciton that determines the low-temperature PL of colloidal nanocrystals are discussed in detail. The radiative recombination of a dark exciton becomes possible as a result of simultaneous flips of the surface spin and electron spin in a dark exciton that leads to admixture of bright exciton states. This recombination mechanism is effective in the case of a disordered state of the spin system and is suppressed if the polaron ferromagnetic state forms. The conditions and various mechanisms of formation of the spin polaron state and possibilities of its experimental detection are discussed. The experimental and theoretical studies of magnetic field-induced circular polarization of PL in ensembles of colloidal nanocrystals are reviewed.

Highly electrically conductive polyethylenedioxythiophene thin films for thermoelectric applications

Enhanced PP-modified PEDOT:Tos based thermoelectrics present increased densities of the polaron state and stabilized densities of the bipolaron state.