E. G. Petrov

BRIDGE-ASSISTED ELECTRON TRANSFER DRIVEN BY DICHOTOMICALLY FLUCTUATING TUNNELING COUPLING

The influence of dichotomically fluctuating tunneling coupling on long‐range electron transfer is studied theoretically. Within an approach similar to the noninteracting blip approximation known from the spin‐boson model a set of coupled integrodifferential kinetic equations is derived. These equations describe the time development of the electronic populations difference between the donor and acceptor states averaged with respect to the stochastic process and the quantum fluctuations of the bath. Furthermore, they contain the correlator between the level population difference and the fluctuating tunneling matrix element. A detailed analysis is carried out for the case of a strong coupling of the transferred electron to a single soft reaction coordinate. Within a Markovian approximation and an adiabatic removing of the correlator, the balance type kinetic equations can be derived which contain effective transfer rates. These rates depend strongly on the correlation time of fluctuations and can exhibit a r...

Control of the dynamics of a dissipative two-level system by a strong periodic field

Abstract The incoherent dynamics of a two-level system (TLS) coupled to a thermal bath and driven by a strong external periodic field is studied. Starting with the master equation for a dissipative TLS in an external field, we derive analytical expressions for the effective rate constant and for the apparent energy bias of the TLS in a fast oscillating periodic field. The expressions obtained include the field in a non-perturbative manner and they are used to study the influence of a strong periodic driving field on long-range electron transfer reactions in condensed media. It is shown that, for some cases, the steady-state populations of the donor and acceptor levels and therefore the direction of electron transfer can be inverted by a strong periodic field.

Control of long-range electron transfer in dynamically disordered molecular systems by an external periodic field

The influence of a strong periodic field on the long-range electron transfer is studied theoretically within the driven spin-boson model extended by a dichotomically fluctuating tunneling coupling. Applying the noninteracting blip approximation, a set of coupled kinetic equations is derived. It describes the time-development of the electronic population difference between the donor and acceptor states averaged with respect to the stochastic process, the quantum fluctuations of the bath and over the fast oscillating field. The strength of the periodic field is taken into account in a nonperturbative manner. A detailed analysis is carried out for the case of a strong coupling of the transferred electron to a specific reaction coordinate. Analytical expressions for the effective transfer rate are obtained and their numerical analysis is presented. For the case of adiabatically controlled (gated) transfer the existence of a transfer regime is demonstrated where the strong external field does not influence the...

Noise-induced current reversal in a stochastically driven dissipative tight-binding model

Abstract The cooperative effects induced by external random dichotomic and d.c. driving are studied for charge drift and diffusion in a one-dimensional dissipative tight-binding model. For a strongly correlated dichotomic field the effect of large diffusion acceleration is demonstrated. Additionally, it is shown that the averaged current direction can be inverted by applying a strongly correlated electric field (noise-induced negative conductivity).

AN EXACT SOLUTION OF THE STOCHASTIC LIOUVILLE EQUATION : THE TWO-LEVEL SYSTEM COUPLED TO AN ASYMMETRIC DICHOTOMOUS FIELD

Abstract Applying the technique of Brissaud and Firsh an exact expression can be derived for the averaged density matrix of the two-level system interacting with an asymmetric dichotomous field. Expressions for the level populations valid at any Kubo number are presented for the energetically degenerated two-level system as well as for the case of a large energy difference between the levels. It can be demonstrated that the asymmetric dichotomous perturbation favors the coherent transfer in the case of an energetically degenerated two-level system and does not result in an asymmetric steady-state population for the non-degenerated case.

Generalized Pauli master equation for a quantum dynamic system in an external field

Abstract Generalization of the Pauli master equation to the case of strong time-dependent fields is obtained. It is shown that time-dependent transition rates are retarded functionals of the non-stationary energy levels of the quantum system. As an example, the role of the fast energetic stochastization in relaxation transitions is considered.