arXiv subjects

S. A. Mikhailov

Publications and source records attributed to S. A. Mikhailov.

At least 37 records · Page 2Linked to original sources

arXiv2015

Reply to Comment on `Theory of microwave-induced zero-resistance states in two-dimensional electron systems' and on `Microwave-induced zero-resistance states and second-harmonic generation in an ultraclean two-dimensional electron gas'

We show that all questions raised in the Comment can be easily answered within the theory formulated in the commented papers. It is also shown that the bulk theory promoted by the commenter fails to explain the most important fundamental features of the discussed phenomenon.

cond-mat.mes-hall↗

arXiv2014

Quantum Theory of the Third-Harmonic Generation in Graphene

A quantum theory of the third-harmonic generation in graphene is presented. An analytical formula for the nonlinear conductivity tensor $σ^{(3)}_{αβγδ}(ω,ω,ω)$ is derived. Resonant maxima of the third harmonic are shown to exist at low frequencies $ω\ll E_F/\hbar$, as well as around the frequency $ω=2E_F/\hbar$, where $E_F$ is the Fermi energy in graphene. At the input power of a CO$_2$ laser ($λ\approx 10$ $μ$m) of about 1 MW/cm$^2$ the output power of the third-harmonic ($λ\approx 3.3$ $μ$m) is expected to be $\simeq 50$ W/cm$^2$.

cond-mat.mes-hall↗

arXiv2014

Nonlinear electromagnetic response of a uniform electron gas

The linear electromagnetic response of a uniform electron gas to a longitudinal electric field is determined, within the self-consistent-field theory, by the linear polarizability and the Lindhard dielectric function. Using the same approach we derive analytical expressions for the second- and third-order nonlinear polarizabilities of the three-, two- and one-dimensional homogeneous electron gases with the parabolic electron energy dispersion. The results are valid both for degenerate (Fermi) and non-degenerate (Boltzmann) electron gases. A resonant enhancement of the second and third harmonics generation due to a combination of the single-particle and collective (plasma) resonances is predicted.

cond-mat.mes-hall↗

arXiv2013

Radiative damping and synchronization in a graphene-based terahertz emitter

We investigate the collective electron dynamics in a recently proposed graphene-based terahertz emitter under the influence of the radiative damping effect, which is included self-consistently in a molecular dynamics approach. We show that under appropriate conditions synchronization of the dynamics of single electrons takes place, leading to a rise of the oscillating component of the charge current. The synchronization time depends dramatically on the applied dc electric field and electron scattering rate, and is roughly inversely proportional to the radiative damping rate that is determined by the carrier concentration and the geometrical parameters of the device. The emission spectra in the synchronized state, determined by the oscillating current component, are analyzed. The effective generation of higher harmonics for large values of the radiative damping strength is demonstrated.

cond-mat.mes-hall↗

arXiv2013

Microwave-induced zero-resistance" states and second-harmonic generation in an ultraclean two-dimensional electron gas

Microwave-induced resistance oscillations (MIRO) and "zero-resistance" states (ZRS) were discovered in ultraclean two-dimensional electron systems in 2001-2003 and have attracted great interest from researchers. A comprehensive theory of these phenomena was developed in 2011: It was shown that all experimentally observed dependencies can be naturally explained by the influence of the ponderomotive forces which arise in the near-contact regions of the two-dimensional electron gas under the action of microwaves. Now we show that the same near-contact physical processes should lead to another nonlinear electrodynamic phenomenon - the second-harmonic generation. We calculate the frequency, magnetic field, mobility, and power dependencies of the second-harmonic intensity and show that it can be as large as ~ 0.5 mW/cm2 under realistic experimental conditions. A part of this paper is devoted to a further discussion of the MIRO/ZRS phenomena: we explain how the ponderomotive-force theory explains different experimental details, including those which were not known in 2011, and critically discuss alternative theories.

cond-mat.mes-hall↗

arXiv2013

Ferroelectric instability of two-dimensional crystals

The macroscopic dielectric permittivity of dielectric crystals is related to the microscopic atomic polarizability of constituent atoms by the known Clausius-Mossotti relation obtained in the middle of 19th century. We derive a similar relation for recently discovered two-dimensional crystals (mono- and bilayer graphene, boron nitride, etc) and show that, in contrast to three-dimensional materials, much stronger electron-electron interaction in two dimensions leads to a spontaneous electric polarization of the ground state of two-dimensional crystals. The predicted ferroelectric transition may have interesting applications in electrodynamics and optics.

cond-mat.mes-hall↗

arXiv2012

Graphene-based voltage-tunable coherent terahertz emitter

A portion of the electromagnetic wave spectrum between $\sim 0.1$ and $\sim 10$ terahertz (THz) suffers from the lack of powerful, effective, easy-to-use and inexpensive emitters, detectors and mixers. We propose a multilayer graphene -- boron-nitride heterostructure which is able to emit radiation in the frequency range $\sim 0.1-30$ THz with the power density up to $\sim 0.5$ W/cm$^2$ at room temperature. The proposed device is extremely thin, light, flexible, almost invisible and may completely cover the needs of science and technology in the sources of terahertz radiation.

cond-mat.mes-hall↗

arXiv2012

Nonlinear broadening of the plasmon linewidth in a graphene stripe

In contrast to semiconductor structures, the experimentally observed plasma resonances in graphene show an asymmetrical and rather broad linewidth. We show that this can be explained by the linear electron energy dispersion in this material and is related to the violation of the generalized Kohn theorem in graphene.

cond-mat.mes-hall↗

arXiv2011

Theory of the giant plasmon enhanced second harmonic generation in graphene and semiconductor two-dimensional electron systems

An analytical theory of the nonlinear electromagnetic response of a two-dimensional (2D) electron system in the second order in the electric field amplitude is developed. The second-order polarizability and the intensity of the second harmonic signal are calculated within the self-consistent-field approach both for semiconductor 2D electron systems and for graphene. The second harmonic generation in graphene is shown to be about two orders of magnitude stronger than in GaAs quantum wells at typical experimental parameters. Under the conditions of the 2D plasmon resonance the second harmonic radiation intensity is further increased by several orders of magnitude.

cond-mat.mes-hall↗

arXiv2011

Theory of the microwave induced zero resistance states in two-dimensional electron systems

The phenomena of the microwave induced zero resistance states (MIZRS) and the microwave induced resistance oscillations (MIRO) were discovered in the ultraclean two-dimensional electron systems in 2001 -- 2003 and have attracted great interest of researchers. In spite of numerous theoretical efforts the true origin of these effects remains unknown so far. We show that the MIRO/ZRS phenomena are naturally explained by the influence of the ponderomotive forces which arise in the near-contact regions of the two-dimensional electron gas under the action of microwaves. The proposed analytical theory is in agreement with all experimental facts accumulated so far and provides a simple and self-evident explanation of the microwave frequency, polarization, magnetic field, mobility, power and temperature dependencies of the observed effects.

cond-mat.mes-hall↗

arXiv2009

Strong nonlinear optical response of graphene flakes measured by four-wave mixing

We present the first experimental investigation of nonlinear optical properties of graphene flakes. We find that at near infrared frequencies a graphene monolayer exhibits a remarkably high third-order optical nonlinearity which is practically independent of the wavelengths of incident light. The nonlinear optical response can be utilized for imaging purposes, with image contrasts of graphene which are orders of magnitude higher than those obtained using linear microscopy.

cond-mat.mtrl-sci↗

arXiv2009

Dielectric function and plasmons in graphene

The electromagnetic response of graphene, expressed by the dielectric function, and the spectrum of collective excitations are studied as a function of wave vector and frequency. Our calculation is based on the full band structure, calculated within the tight-binding approximation. As a result, we find plasmons whose dispersion is similar to that obtained in the single-valley approximation by Dirac fermions. In contrast to the latter, however, we find a stronger damping of the plasmon modes due to inter-band absorption. Our calculation also reveals effects due to deviations from the linear Dirac spectrum as we increase the Fermi energy, indicating an anisotropic behavior with respect to the wave vector of the external electromagnetic field.

cond-mat.str-el↗

arXiv2009

Revision of the theory of a uniform electron gas

The many-body theory of a uniform electron gas was developed at the end of 1950ies. The Coulomb interaction between electrons was considered as a perturbation and the ground state energy was calculated in all orders of the non-degenerate perturbation theory. We show that the ground state of the unperturbed system is actually strongly degenerate and that the degenerate perturbation theory leads to lower values of the ground state energy.

cond-mat.str-el↗

arXiv2008

Non-linear effects in the cyclotron resonance of a massless quasi-particle in graphene

We consider the classical motion of a massless quasi-particle in a magnetic field and under a weak electromagnetic radiation with the frequency $ω$. Due to the non-parabolic, linear energy dispersion, the particle responds not only at the frequency $ω$ but generates a broad frequency spectrum around it. The linewidth of the cyclotron resonance turns out to be very broad even in a perfectly pure material which allows one to explain recent experimental data in graphene. It is concluded that the linear response theory does not work in graphene in finite magnetic fields.

cond-mat.mes-hall↗

arXiv2008

Non-linear graphene optics for terahertz applications

The linear electrodynamic properties of graphene -- the frequency-dependent conductivity, the transmission spectra and collective excitations -- are briefly outlined. The non-linear frequency multiplication effects in graphene are studied, taking into account the influence of the self-consistent-field effects and of the magnetic field. The predicted phenomena can be used for creation of new devices for microwave and terahertz optics and electronics.

cond-mat.mes-hall↗

arXiv2008

Nonlinear electromagnetic response of graphene: Frequency multiplication and the self-consistent-field effects

Graphene is a recently discovered carbon based material with unique physical properties. This is a monolayer of graphite, and the two-dimensional electrons and holes in it are described by the effective Dirac equation with a vanishing effective mass. As a consequence, electromagnetic response of graphene is predicted to be strongly non-linear. We develop a quasi-classical kinetic theory of the non-linear electromagnetic response of graphene, taking into account the self-consistent-field effects. Response of the system to both harmonic and pulse excitation is considered. The frequency multiplication effect, resulting from the non-linearity of the electromagnetic response, is studied under realistic experimental conditions. The frequency up-conversion efficiency is analysed as a function of the applied electric field and parameters of the samples. Possible applications of graphene in terahertz electronics are discussed.

cond-mat.mes-hall↗

arXiv2007

Non-linear self-consistent response of graphene in time domain

We study the non-linear electromagnetic response of graphene taking into account the self-consistent-field effects. Response of the system to a strong pulse excitation is calculated. It is shown that radiative decay in graphene differs from that of conventional two-dimensional electron systems both quantitatively and qualitatively. Possible applications of the predicted effects for generation of terahertz radiation are discussed.

cond-mat.mes-hall↗

arXiv2007

Non-linear electromagnetic response of graphene

It is shown that the massless energy spectrum of electrons and holes in graphene leads to the strongly non-linear electromagnetic response of this system. We predict that the graphene layer, irradiated by electromagnetic waves, emits radiation at higher frequency harmonics and can work as a frequency multiplier. The operating frequency of the graphene frequency multiplier can lie in a broad range from microwaves to the infrared.

cond-mat.mes-hall↗