arXiv subjects

Natalya A. Zimbovskaya

Publications and source records attributed to Natalya A. Zimbovskaya.

At least 19 recordsLinked to original sources

arXiv2026

The effect of light scattering in cavity electrodynamics: Fresnel equations with decoherence

We consider the effect of light decoherence in a Fabri-Perot (FP) microcavity. We show that, when present, it may significantly change its linear response to the incident light.The optical properties of the bounding mirrors are described using the classical electrodynamics, and the light scattering causing the phase breaking is treated as a multichannel scattering problem employing a model introduced by Büttiker to describe dephasing in electron transport. We show that the dephasing causes a gradual erosion of the cavity photon mode and thus impedes the formation of molecular polaritons. Consequently, the polaritons signatures in the transmission and absorption optical spectra of the microcavity are fading away as the scattering intensifies.

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arXiv2026

The effect of Coulomb interactions of thermoelectric characteristics of Marcus molecular junctions

We present a theoretical study focused on the influence of Coulomb interactions on thermoelectric properties of molecular junctions assuming that electron transport is strongly affected by thermalized phonon modes in the molecular ambient. It is shown that the combined effect of Coulomb interactions between electrons on the molecular states and the reorganization processes in the ambient may significantly affect both Seebeck coefficient and the power factor. Specifically, we show that electron-electron interactions may counter-balance the effect of the ambient molecules reorganizations resulting in qualitative changes in the behavior of both zero-bias conductance and thermopower.

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arXiv2024

Thermoelectric properties of Marcus molecular junctions

In the present work we theoretically analyze thermoelectric transport in single-molecule junctions (SMJ) characterized by strong interactions between electrons on the molecular linkers and phonons in their nuclear environments where electron hopping between the electrodes and the molecular bridge states predominates in the steady state electron transport. The analysis is based on the modified Marcus theory accounting for the lifetime broadening of the bridge's energy levels. We show that the reorganization processes in the environment accompanying electron transport may significantly affect SMJ thermoelectric properties both within and beyond linear transport regime. Specifically, we study the effect of environmental phonons on the electron conductance, the thermopower and charge current induced by the temperature gradient applied across the system.

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arXiv2023

Heat currents in a two channel Marcus molecular junction

We present a theoretical analysis of heat transport through a single-molecule junction with two possible transport channels for electrons where interactions between electrons on the molecule and phonons in the nuclear environment is strong and Marcus-type processes predominate in the electron transport. We show that within the steady state regime the competition between transport channels may result in negative differential heat conductance and cooling of the molecule environment. Also, we analyze the effect of a slowly driven molecule level (provided that another level is fixed) on the heat transport and power generated in the system.

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arXiv2022

Fano effect in a thermally induced transport through a triple quantum dot within the Coulomb blockade regime

In the present work we theoretically study thermoelectric transport and heat transfer in a junction including a $T$-shaped double quantum dot coupled to nonmagnetic electrodes and supplemented with a third dot in a parallel configuration. We focus on the combined effect of Coulomb interactions and quantum interference occurring in the $T$-shaped portion of the considered triple quantum dot on the thermoelectric electron transport. The transport through the system is studied within the Coulomb blockade regime in the limit of strong intra-dot interactions between electrons beyond the linear response regime. It is shown that under these conditions both charge and heat transfer through the considered system may be significantly affected by the quantum interference and inter-dot Coulomb interactions.

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arXiv2020

Energy, work, entropy and heat balance in Marcus molecular junctions

We present a consistent theory of energy balance and conversion in a single-molecule junction with strong interactions between electrons on the molecular linker (dot) and phonons in the nuclear environment where the Marcus-type electron hopping processes predominate in the electron transport. It is shown that the environmental reorganization and relaxation that accompany electron hopping energy exchange between the electrodes and the nuclear (molecular and solvent) environment may bring a moderate local cooling of the latter in biased systems. The effect of a periodically driven dot level on the heat transport and power generated in the system is analyzed and energy conservation is demonstrated both within and beyond the quasistatic regime. Finally, a simple model of atomic scale engine based on a Marcus single-molecule junction with a driven electron level is suggested and discussed.

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arXiv2018

Thermoelectric efficiency of single-molecule junctions with long molecular linkers

We report results of theoretical studies of thermoelectric efficiency of single-molecule junctions with long molecular linkers. The linker is simulated by a chain of identical sites described using a tight-binding model. It is shown that thermoelectric figure of merit ZT strongly depends on the bridge length, being controlled by the lineshape of electron transmission function within the tunnel energy range corresponding to HOMO/LUMO transport channel. Using the adopted model we demonstrate that ZT may significantly increase as the linker lengthens, and that gateway states on the bridge (if any) may noticeably affect the length-dependent ZT. Temperature dependences of ZT for various bridge lengths are analyzed. It is shown that broad minima emerge in ZT versus temperature curves whose positions are controlled by the bridge lengths.

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arXiv2018

Thermally induced charge current through long molecules

In this work we theoretically study steady state thermoelectric transport through a single-molecule junction with a long chain-like bridge. Electron transmission through the system is computed using a tight-binding model for the bridge. We analyze dependences of thermocurrent on the bridge length in unbiased and biased systems operating within and beyond linear response regime. It is shown that length-dependent thermocurrent is controlled by the lineshape of electron transmission in the interval corresponding to HOMO/LUMO transport channel. Also, it is demonstrated that electron interactions with molecular vibrations may significantly affect length-dependent thermocurrent.

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arXiv2017

Temperature dependent charge transport mechanisms in carbon sphere/polymer composites

Carbon spheres (CS) with diameters in the range $2 - 10 μm$ were prepared via hydrolysis of a sucrose solution at $200^o C,$ and later annealed in $N_2$ at $800^o C.$ The spheres were highly conducting but difficult to process into thin films or pressed pellets. In our previous work, composite samples of CS and the insulating polymer polyethylene oxide (PEO) were prepared and their charge transport was analyzed in the temperature range $ 80 K < T < 300 K. $ Here, we analyze charge transport in CS coated with a thin polyaniline (PANi) film doped with hydrochloric acid (HCl), in the same temperature range. The goal is to study charge transport in the CS using a conducting polymer (PANi) as a binder and compare with that occurring at CS/PEO. A conductivity maxima was observed in the CS/PEO composite but was absent in CS/PANi. Our data analysis shows that variable range hopping of electrons between polymeric chains in PANi-filled gaps between CS takes on a predominant part in transport through CS/PANi composites, whereas in CS/PEO composites, electrons travel through gaps between CS solely by means of direct tunneling. This difference in transport mechanisms results in different temperature dependences of the conductivity.

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arXiv2017

Modeling of a self-sustaining ignition in a solid energetic material

In the present work we analyze some necessary conditions for ignition of solid energetic materials by low velocity impact ignition mechanism. Basing on reported results of {\it ab initio} computations we assume that the energetic activation barriers for the primary endothermic dissociation in some energetic materials may be locally lowered due to the effect of shear strain caused by the impact. We show that the ignition may be initiated in regions with the reduced activation barriers, even at moderately low exothermicity of the subsequent exothermic reactions thus suggesting that the above regions may serve as "hot spots" for the ignition. We apply our results to analyze initial steps of ignition in DADNE and TATB molecular crystals.

cond-mat.mtrl-sci↗

arXiv2017

Length-dependent Seebeck effect in single-molecule junctions beyond linear response regime

In the present work we theoretically study characteristics of nonlinear Seebeck effect in a single-molecule junction with chain-like bridge of an arbitrary length. We have employed tight-binding models to compute electron transmission trough the system. We concentrate on analysis of dependences of thermovoltage $V_{th} $ and differential thermopower $ S $ on the bridge length. It is shown that $ V_{th} $ becomes stronger and $ S $ grows as the bridge lengthens. We discuss the effects of the bridge coupling to the electrodes and of specific characteristics of terminal sites on the bridge on the length-dependent $ V_{th} $ and $ S $ which appear when the system operates beyond linear response regime.

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arXiv2016

Length-dependent thermopower of single-molecule junctions

In the present work we theoretically study the length dependence of thermopower of a single-molecule junction with a chain-like molecular bridge of an arbitrary length using a tight-binding model. We analyze conditions bringing a nonlinear growth of the thermopower accompanying the extension of the bridge length. Also, we show that the thermopower may decrease with increasing molecular length provided that the molecular bridge is sufficiently long.

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arXiv2016

Electron transport mechanisms in polymer-carbon sphere composites

A set of uniform carbon microspheres (CS) whose diameters have the order of $ 0.125 μm$ to $10 μm $ was prepared from aqueous sucrose solution by means of hydrothermal carbonization of sugar molecules. A pressed pellet was composed by mixing CSs with polyethylene oxide (PEO). Electrical characterization of the pellet was carried out showing Ohmic current-voltage characteristics and temperature-dependent conductivity in the range $ 80K < T < 300K.$ The conductivity reached a maximum value of $ 0.245 S/cm $ at $ 258K. $ The dependence of conductivity on temperature was theoretically analyzed to determine predominating mechanisms of electron transport. It was shown that thermally-induced electron tunneling between adjacent spheres may take on an important part in the electron transport through the CS/PEO composites.

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arXiv2016

Nonlinear thermoelectric transport in single-molecule junctions: the effect of electron-phonon interactions

In the present work, we theoretically analyze the steady-state thermoelectric transport through a single-molecule junction with a vibrating bridge. Thermally induced charge current in the system is explored using a nonequilibrium Green's functions formalism. We study combined effects of Coulomb interactions between charge carriers on the bridge and electron-phonon interactions on the thermocurrent beyond the linear response regime. It is shown that electron-vibron interactions may significantly affect both magnitude and direction of the thermocurrent, and vibrational signatures may appear.

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arXiv2015

Scattering theory of thermocurrent in quantum dots and molecules

In this work we theoretically study properties of electric current driven by a temperature gradient through a quantum dot/molecule coupled to the source and drain charge reservoirs. We analyze the effect of Coulomb interactions between electrons on the dot/molecule and of thermal environment on the thermocurrent. The environment is simulated by two thermal baths associated with the reservoirs and kept at different temperatures. The scattering matrix formalism is employed to compute electron transmission through the system. This approach is further developed and combined with nonequilibrium Green's functions formalism, so that scattering probabilities are expressed in terms of relevant energies including the thermal energy, strengths of coupling between the dot/molecule and charge reservoirs and characteristic energies of electron-phonon interactions. It is shown that one may bring the considered system into regime favorable for heat-to-electric energy conversion by varying the applied bias and gate voltages.

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arXiv2015

The effect of Coulomb interactions on nonlinear thermovoltage and thermocurrent in quantum dots

In the present work, we theoretically study the nonlinear regime of charge transport through a quantum dot coupled to the source and drain reservoirs. The investigation is carried out using a nonequilibrium Green's functions formalism beyond the Hartree-Fock approximation. Employed approximations for the relevant Green's functions allow to trace a transition from Coulomb blockade regime to Kondo regime in the thermoelectric transport. Effects arising when electrons move in response to thermal gradient applied across the system are discussed, including experimentally observed thermovoltage zeros.

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arXiv2014

The effect of dephasing on thermoelectric efficiency of molecular junctions

In this work we report the results of theoretical analysis of the effect of thermal environment on the thermoelectric efficiency of molecular junctions. The environment is represented by two thermal phonon baths associated with the electrodes which are kept at different temperatures. The analysis is carried out using the Buttiker model within the scattering matrix formalism to compute electron transmission through the system. This approach is further developed, so that the dephasing parameters are expressed in terms of relevant energies including the thermal energy, strengths of coupling between the molecular bridge and the electrodes and characteristic energies of electron-phonon interactions. It is shown that the latter significantly affect thermoelectric efficiency by destroying coherency of the electron transport through the considered system.

cond-mat.mtrl-sci↗

arXiv2014

The effect of Coulomb interactions on thermoelectric properties of quantum dots

Thermoelectric effects in a quantum dot coupled to the source and drain charge reservoirs are explored using a nonequilibrium Green's functions formalism beyond the Hartree-Fock approximation. Thermal transport is analyzed within a linear response regime. A transition from Coulomb blockade regime to Kondo regime in thermoelectric transport through a single-level quantum dot is traced using unified approximations for the relevant Green's functions.

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