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Natalya A. Zimbovskaya

Publications and source records attributed to Natalya A. Zimbovskaya.

52 records · Page 3Linked to original sources
arXiv2006

Local Features of the Fermi Surface Curvature and the Anomalous Skin Effect in Metals

In this paper we present a theoretical analysis of the effect of local geometrical structure of the Fermi surface on the surface impedance of a metal at the anomalous skin effect. We show that when the Fermi surface includes nearly cylindrical and/or flattened segments it may significantly change both magnitude and frequency dependence of the surface impedance. Being observed in experiments these unusual frequency dependencies could bring additional information concerning fine geometrical features of the Fermi surfaces of metals.

cond-mat.mtrl-sci↗
arXiv2006

Fermi-liquid theory of the surface impedance of a metal in a normal magnetic field

In this paper we present detailed theoretical analysis of the frequency and/or magnetic field dependence of the surface impedance of a metal at the anomalous skin effect. We calculate the surface impedance in the presence of a magnetic field directed along the normal to the metal surface. The effects of the Fermi-liquid interactions on the surface impedance are studied. It is shown that the cyclotron resonance in a normal magnetic field may be revealed {\it only and exclusively} in such metals whose Fermi surfaces include segments where its Gaussian curvature turns zero. The results could be applied to extract extra informations concerning local anomalies in the Fermi surface curvature in conventional and quasi-two-dimensional metals.

cond-mat.mtrl-sci↗
arXiv2005

Local Flattening of the Fermi Surface and Quantum Oscillations in the Magnetoacoustic Response of a Metal

In the present work we theoretically analyze the effect of the Fermi surface local geometry on quantum oscillations in the velocity of an acoustic wave travelling in metal across a strong magnetic field. We show that local flattenings of the Fermi surface could cause significant amplification of quantum oscillations. This occurs due to enhancement of commensurability oscillations modulating the quantum oscillations in the electron density of states on the Fermi surface. The amplification in the quantum oscillations could be revealed at fitting directions of the magnetic field.

cond-mat.mtrl-sci↗
arXiv2005

Local Geometry of the Fermi Surface and Quantum Oscillations in the Linear Response of Metals

In this paper we present a theoretical analysis of the effect of anomalies of the Fermi surface (FS) curvature on oscillations in the electron density of states (DOS) in strong magnetic fields. It is shown that the oscillations could be significantly strengthened when the FS curvature turns zero in the vicinities of some extremal cross sections, and they could be weakened when the curvature takes on extremely large values or diverges there. This leads to a characteristic dependence of the oscillations magnitude on the direction of the magnetic field which is studied. The results of these general studies are employed to analyze the effects of the FS curvature anomalies on the quantum oscillations in the velocity of sound waves travelling in metals.

cond-mat.mtrl-sci↗
arXiv2005

Low Temperature Electronic Transport and Electron Transfer through Organic Macromolecules

It is shown that at low temperatures and moderate electron dephasing the electron transmission function reveales a structure containing information about donor/acceptor sites effectively participating in the electron transfer (ET) processes and primary pathways of electrons tunneling through molecular bridges in macromolecules. This important information can be obtained as a result of analysis of experimental low temperature current-voltage characteristics for chosen molecules.

physics.bio-ph↗
arXiv2005

On the Electronic Transport Mechanism in Conducting Polymer Nanofibers

Here, we present theoretical analysis of electron transport in polyaniline based (PANi) nanofibers assuming the metalic state of the material. To build up this theory we treat conducting polymers as a special kind of granular metals, and we apply the quantum theory of conduction in mesoscopic systems to describe the transport between metallic-like granules. Our results show that the concept of resonance electron tunneling as the predominating mechanism providing charge transport between the grains is supported with recent experiments on the electrical characterization of single PANi nanofibers. By contacting the proposed theory with the experimental data we estimate some important parameters characterizing the electron transport in these materials. Also, we discuss the origin of rectifying features observed in current-voltage characteristics of fibers with varying cross-sectional areas.

cond-mat.soft↗
arXiv2005

Electrodynamics of Nearly-Ferroelectric Superconductors

We report here the frequency-dependent optical response of a nearly ferroelectric superconductor (NFE-SC), like Na$_{x}$WO$_3$, or n-SrTiO$_3$. From $ω=0$, up to a critical frequency $ ω_{c1}$, Meissner-like field extinction occurs as in a usual superconductor. In the "anomalous" region $ω_{c1}<ω<ω_{TO}$ (the TO frequency of the NFE) the field propagates as in a dielectric. For $ω>ω_{TO}$ Meissner damping recurrs, then at higher $ω$, dielectriclike propagation is found. New optical anomalies (peaks in transmission) are predicted for a film of NFE-SC below the soft mode frequency $ω_{TO}$. These effects are due to including the contribution of the NFE displacement current in the solution of the coupled Maxwell, lattice and London equations. Quantitative calculations are given for the NFE-SC n-SrTiO$_3 $ to illustrate this.

cond-mat.supr-con↗
arXiv2005

Low Temperature Electronic Transport through Macromolecules and Characteristics of Intramolecular Electron Transfer

A theory of electronic transport through molecular wires is applied to analyze characteristics of a long-range electron transfer (ET) through molecular bridges in macromolecules with complex donor/acceptor subsystems. Assuming a coherent electron tunneling through the bridge to be the predominant mechanism of ET at low temperatures it is shown that low temperature current-voltage curves can exhibit a step-like structure, which contains information concerning intrinsic features of ET processes such as the effect of donor/acceptor coupling to the bridge and primary pathways of electrons tunneling through the bridge. By contacting the proposed theoretical analysis with such experimental data a variety of valuable characteristics of long-range intramolecular ET can be identified. Analytical and numerical results are presented. Using the Buttiker dephasing model within the scattering matrix formalism we analyze dephasing effects, and we show that these effects could be reduced enough to allow the structure of the electron transmission function to be exposed in the experiments on the electronic transport through macromolecules.

cond-mat.soft↗
arXiv2005

Local Geometry of the Fermi Surface and the Cyclotron Resonance in Metals in a Normal Magnetic Field

In this paper we present a detailed theoretical analysis of the cyclotron resonance in metals in the magnetic field directed along a normal to the surface of a sample. We show that this resonance occurs due to local geometry of the Fermi surface of a metal. When the Fermi surface (FS) includes segments where its curvature turns zero or diverges, this could give rise to resonance features in the frequency/magnetic field dependence of the surface impedance or its derivative with respect to the field. Otherwise the resonance is scarcely detectable unlike the well-known cyclotron resonance in a parallel magnetic field. The proposed theory agrees with experimantal results concerning both convenient and organic metals.

cond-mat.mtrl-sci↗
arXiv2005

Theory of the dc Magnetotransport in Laterally Modulated Quantum Hall Systems Near Filling $ν={1/2}$

A quasiclassical theory for dc magnetotransport in a modulated quantum Hall system near filling factor $ν={1/2}$ is presented. A weak one-dimensional electrostatic potential acts on the two-dimensional electron gas. Closed form analytic expressions are obtained for the resistivity $ρ_\perp$ corresponding to a current at right angles to the direction of the modulation lines as well as a smaller component $ρ_{||}$ for a current along the direction of the modulation lines. It is shown that both resistivity components are affected by the presence of the modulation. Numerical results are presented for $ρ_\perp$ and $ρ_{||}$ and show reasonable agreement with the results of recent experiments.

cond-mat.mes-hall↗
arXiv2005

The Effect of a Magnetic Field on the Acoustoelectric current in a Narrow Channel

The effect of a perpendicular magnetic field on the quantized current induced by a surface acoustic wave in a quasi-1D channel is studied. The channel has been produced experimentally in a GaAs heterostructure by shallow etching techniques and by the application of a negative gate voltage to Schottky split gates. Commensurability oscillations of the quantized current in this constriction have been observed in the interval of current between quantized plateaus. The results can be understood in terms of a moving quantum dot with the electron in the dot tunneling into the adjacent two-dimensional region. The goal is to explain qualitatively the mechanism for the steplike nature of the acoustoelectric current as a function of gate voltage and the oscillations when a magnetic field is applied. A transfer Hamiltonian formalism is employed.

cond-mat.mes-hall↗
arXiv2005

On the Theory of Magnetotransport in a Periodically Modulated Two-Dimensional Electron Gas

A semiclassical theory based on the Boltzmann transport equation for a two-dimensional electron gas modulated along one direction with weak electrostatic or magnetic modulations is proposed. It is shown that oscillations of the magnetoresistivity $ ρ_{||} $ corresponding to the current driven along the modulation lines observed at moderately low magnetic fields, can be explained as classical geometric resonances reflecting the commensurability of the period of spatial modulations and the cyclotron radius of electrons.

cond-mat.mes-hall↗
arXiv2005

Quantum Oscillations of Elastic Moduli and Softening of Phonon Modes in Metals

In this paper we present a theoretical analysis of the effect of magnetostriction on quantum oscillations of elastic constants in metals under strong magnetic fields. It is shown that at low temperatures a significant softening of some acoustic modes could occur near peaks of quantum oscillations of the electron density of states (DOS) at the Fermi surface (FS). This effect is caused by a magnetic instability of a special kind, and it can give rise to a lattice instability. We also show that the most favorable conditions for this instability to be revealed occur in metals whose Fermi surfaces include nearly cylindrical segments.

cond-mat.mtrl-sci↗
arXiv2004

Local Geometry of the Fermi Surface and Magnetoacoustic Responce of Two-Dimensional Electron Systems in Strong Magnetic Fields

A semiclassical theory for magnetotrasport in a quantum Hall system near filling factor $ν= 1/2 $ based on the Composite Fermions physical picture is used to analyze the effect of local flattening of the Composite Fermion Fermi surface (CF-FS) upon magnetoacoustic oscllations. We report on calculations of the velocity shift and attenuation of a surface acoustic wave (SAW) which travels above the two-dimensional electron system, and we show that local geometry of the CF-FS could give rise to noticeable changes in the magnitude and phase of the oscillations. We predict these changes to be revealed in experiments, and to be used in further studies of the shape and symmetries of the CF-FS. Main conclusions reported here could be applied to analyze magnetotransport in quantum Hall systems at higher filling factors $ ν= 3/2, 5/2 $ provided the Fermi-liquid-like state of the system.

cond-mat.mes-hall↗
arXiv2003

Microwave Rectificatin of the Current at the Metal-Metal Junction for Dilute 2D Metals

Within a quasiclassical transport theory for 2D electron system we analyze a recently observed effect of microwave rectification at the boundary between two 2D metals of different carrier densities. Nonlinear response is employed to explain the effect. It is shown that the effect of rectification arises due to inhomogeneity of the electron density which breaks space symmetry of the system. The results agree with the above experiments.

cond-mat.mes-hall↗