arXiv subjects

I. V. Oladyshkin

Publications and source records attributed to I. V. Oladyshkin.

5 recordsLinked to original sources

arXiv2022

Optical properties of graphane in infrared range

The theory of optical effects in hydrogenated graphene (graphane) in terahertz and infrared range is developed, including the analysis of complex conductivity, reflection coefficient for graphane on a substrate and dispersion of surface plasmon-polaritons. The calculations are based on quite simple analytical approximation of graphane band structure in the vicinity of Gamma-point and on the modified model of quantum coherence relaxation. Comparison of the obtained theoretical results with corresponding experimental data can be used both for the determination of graphane characteristics (Fermi level, relaxation rate etc.) and for the investigation of potential applications of this material in the design of new optical elements.

cond-mat.mes-hall↗

arXiv2022

Polarized light emission from graphene induced by terahertz pulses

Spontaneous optical emission of graphene irradiated by intense single-cycle terahertz pulses was investigated experimentally and explained theoretically. We found that emitted photons are polarized predominantly perpendicular to the electric field of the terahertz pulse, which proves that the terahertz field not only heats the electrons, but also creates a strongly nonequilibrium momentum distribution. Comparison of the measured optical spectrum and polarization anisotropy with the results of numerical modeling allowed us to estimate a momentum isotropization time for electrons in graphene to be ~25 fs and roughly reconstruct the distribution function evolution in k-space.

cond-mat.mes-hall↗

arXiv2020

Magnetic dipole absorption of light at intersubband transitions in quantum wells

We consider theoretically magnetic dipole mechanism of the IR-light absorption at intersubband transitions in wide-gap quantum wells (QW). In contrast to the electric dipole resonance, discussed mechanism manifests in the interaction with the s-polarized component of electromagnetic radiation. We demonstrated that a) the frequencies of magnetic and electric dipole intersubband transitions in 2D layer are equal in the framework of one-particle approximation; b) collective plasma effects should lead to a significant frequency shift between the magnetic and electric dipole resonances in typical QW. That is why independent measurements of the magnetic and electric dipole resonant frequencies could allow both the extracting the QW parameters and the experimental verifying of theoretical models of collective fermion interaction. Taking into account relative weakness of the magnetic dipole absorption, we propose a waveguide scheme for its experimental observation.

cond-mat.mes-hall↗

arXiv2020

Magnetic field inside the metal induced by anisotropic electronic pressure

We show theoretically that anisotropy of electronic distribution function inside the laser-irradiated metal leads to the formation of edge currents at the timescale of distribution isotropization. When the electronic pressure in the skin-layer is anisotropic, pressure gradient appears to be non-potential force effectively producing low-frequency magnetic field. In typical experiments with femtosecond laser pumping generated internal magnetic field can rich magnitude up to ~1 Tesla in non-damaging interaction regime. We demonstrate that this field is localized inside the metal, while just a minor part of its energy can be radiated into free space as a sub-terahertz signal.

physics.optics↗

arXiv2017

Optical emission of graphene and electron-hole pair production induced by a strong THz field

We report on the first experimental observation of graphene optical emission induced by the intense THz pulse. P-doped CVD graphene with the initial Fermi energy of about 200 meV was used, optical photons was detected in the wavelength range of 340-600 nm. Emission started when THz field amplitude exceeded 100 kV/cm. For THz fields from 200 to 300 kV/cm the temperature of optical radiation was constant, while the number of emitted photons increased several dozen times. This fact clearly indicates multiplication of electron-hole pairs induced by an external field itself and not due to electron heating. The experimental data are in a good agreement with the theory of Landau-Zener interband transitions. It is shown theoretically that Landau-Zener transitions are possible even in the case of heavily doped graphene because the strong THz field removes quasiparticles from the region of interband transitions during several femtoseconds, which cancels the Pauli blocking effect.

cond-mat.mes-hall↗