arXiv subjects

Yu. A. Firsov

Publications and source records attributed to Yu. A. Firsov.

7 recordsLinked to original sources

arXiv2017

SERS Mechanism on Graphene

The paper presents briefly some general points of the theory of Surface Enhanced Raman Scattering on metals, semiconductors, dielectrics and graphene. It is pointed out that the reason of SERS on graphene and some other 2D materials is not the chemical enhancement mechanism as it is widely accepted in literature, but ripples, which are necessarily present on a graphene surface and are analogues of the surface roughness, which is a reason of SERS. In addition, it is indicated that the quadrupole interaction, which arises in strong SERS is practically absent in the system with graphene. The results are confirmed by the analysis of the SERS, usual Raman and IR spectra of phthalocyanine molecule and by some other experimental data.

physics.optics↗

arXiv2015

Nanoantenna properties of graphene membrane. Quantum theory

The graphene membrane irradiated by weak activating alternative electric field in terahertz range was considered. The quantum approach based on the time-dependent density matrix method was used. The exact solution was obtained for graphene membrane density matrix equation in linear on the external field approximation. The graphene electromagnetic response was studied i.e. the formulae for the induced current and conductivity were found and analyzed neglecting loss. The obtained formula for the conductivity showed that the graphene membrane was an oscillating contour and its fundamental eigen frequency coincided with a singularity point of the conductivity. This formula allowed us to calculate the graphene membrane inductivity and the capacitance. So the graphene membrane could be used as an antenna or a transistor. It was shown that its eigen frequency could be tuned by doping as its value was found to depend on electrons concentration. It was obtained that the eigen frequency could be tuned in a rather large frequency range 1-100 terahertz as electrons concentration in graphene may differ considerably. The found dependence on concentration correlates with experiments. It would be useful to take the obtained results into account when constructing devices containing graphene membrane nanoantenna allowing wireless communications among nanosystems. This could be promising research area of energy harvesting applications.

cond-mat.mes-hall↗

arXiv2014

Radiative decay effects influence the local electromagnetic response of the monolayer graphene with surface corrugations in terahertz range

We continue the study of surface corrugations influence on the monolayer graphene local electromagnetic response in terahertz range we started earlier. The effects of radiative decay, double-valley structure of charge carriers spectrum in graphene and the breathing surface curvature form induced synthetic electric fields are taken into account. To fulfill this program the generalized nonlinear self-consistent equation is obtained. In case of weak external alternating electric field for the obtained equation in linear approximation on the external electric field the exact solution is found. It shows that in this case we get local dephasing in induced current paths depending on the surface form . This theoretical result qualitatively explains the corresponding experiments with local current patterns in graphene without using fully quantum approach which is necessary for theoretical description of such phenomenon in graphene nanoribbons. Besides the formulae obtained in the present paper could become the basis of the new method of the imaging of surface corrugations form for given picture of local current paths. The obtained results allow to study mechanical behavior of materials at nanoscale deviates from macroscoping established concepts and this is of particular importance for graphene.

cond-mat.mes-hall↗

arXiv2014

Surface corrugations influence on monolayer graphene electromagnetic response

We consider the corrugated monolayer graphene membrane electromagnetic (from both valleys) response in terahertz range. We study the generated in irradiated graphene total current for the first time taking into account both the synthetic electric fields arising due to the (inevitable) presence in graphene of inherent out-of-plane nanodeformations and the double-valleys energy spectrum of Dirac charge particles. Our approach is based on atomistic quantum mechanics used for the description of valence $π-σ$ bonds changes generated by activating external periodic electric field and also for mechanism of Dirac electron interaction with this time-dependent perturbation. We consider the problem in the framework of the model of noninteracting Dirac electrons. Assuming surface corrugations not to be very rough we obtain for weak fields the formula for the total current induced in graphene membrane. Our formula describes the curved current lines in the linear in $E^{ext}(t)$ approximation for the given graphene surface form. We show that the local direction of current lines is determined by synthetic electric field whose direction may essentially differ from the one of the external field and depends on the local curvature of the graphene membrane. We also demonstrate that valley currents generated by the external field have nonzero elliptic polarization angles depending on the point (x,y). Valley currents are shown to rotate in opposite directions in different valleys. The results obtained below can be applied to the analysis of different devices in terahertz optics and optoelectronics and the imaging experiments at the Dirac point.

cond-mat.mes-hall↗

arXiv2002

Unconventional magnetoresistance in long InSb nanowires

Magnetoresistance in long correlated nanowires of degenerate semiconductor InSb in asbestos matrix (wire diameter of around 5 nm, length 0.1 - 1 mm) is studied over temperature range 2.3 - 300 K. At zero magnetic field the electric conduction $G$ and the current-voltage characteristics of such wires obey the power laws $G\propto T^α$, $I\propto V^β$, expected for one-dimensional electron systems. The effect of magnetic field corresponds to a 20% growth of the exponents $α$, $β$ at H=10 T. The observed magnetoresistance is caused by the magnetic-field-induced breaking of the spin-charge separation and represents a novel mechanism of magnetoresistance.

cond-mat.str-el↗

arXiv1999

Luttinger-liquid-like transport in long InSb nanowires

Long nanowires of degenerate semiconductor InSb in asbestos matrix (wire diameter is around 50 Å, length 0.1 - 1 mm) were prepared. Electrical conduction of these nanowires is studied over a temperature range 1.5 - 350 K. It is found that a zero-field electrical conduction is a power function of the temperature $G\propto T^α$ with the typical exponent $α\approx 4$. Current-voltage characteristics of such nanowires are found to be nonlinear and at sufficiently low temperatures follows the power law $I\propto V^β$. It is shown that the electrical conduction of these nanowires cannot be accounted for in terms of ordinary single-electron theories and exhibits features expected for impure Luttinger liquid. For a simple approximation of impure LL as a pure one broken into drops by weak links, the estimated weak-link density is around $10^3-10^4$ per cm.

cond-mat.str-el↗

arXiv1999

Comment on `Dynamical properties of small polarons'

We show that the conclusion on the breakdown of the standard small polaron theory made recently by E.V. deMello and J. Ranninger (Phys. Rev. B 55, 14872 (1997)) is a result of an incorrect interpretation of the electronic and vibronic energy levels of the two-site Holstein model. The small polaron theory, when properly applied, agrees well with the numerical results of these authors. Also we show that their attempt to connect the properties of the calculated correlation functions with the features of the intersite electron hopping is unsuccessful.

cond-mat.supr-con↗