arXiv subjects

Georgy Alymov

Publications and source records attributed to Georgy Alymov.

10 recordsLinked to original sources

arXiv2026

Lamb Shift of Landau Levels in Two-Dimensional Electron Systems in a Multimode Resonator

The use of resonators to modify the behavior of electromagnetic systems demonstrates its potential for application in a wide range of problems. However, existing theoretical studies often resort to the single-mode approximation, rarely considering a second resonator mode. In this paper, we show that including a large number of resonator modes in the model significantly enhances the softening effect of the cyclotron frequency of a two-dimensional electron system. We address this problem by demonstrating the possibility of reducing the system to a set of coupled harmonic oscillators and finding the eigenfrequencies of the oscillators. This is made possible by applying the self-energy method for modes in one polarization and the method for finding the eigenvalues of matrices that have undergone first-rank updating for modes in the perpendicular polarization.

cond-mat.mes-hall↗

arXiv2025

Physical quantities as a partially additive field

We generalize the concept of a field by allowing addition to be a partial operation. We show that elements of such a "partially additive field" share many similarities with physical quantities. In particular, they form subsets of mutually summable elements (similar to physical dimensions), dimensionless elements (those summable with 1) form a field, and every element can be uniquely represented as a product of a dimensionless element and any non-zero element of the same dimension (a unit). We also discuss the conditions for the existence of a coherent unit system. In contrast to previous works, our axiomatization encompasses quantities, values, units, and dimensions in a single algebraic structure, illustrating that partial operations may provide a more elegant description of the physical world.

math-ph↗

arXiv2023

One-dimensional electron localization in semiconductors coupled to electromagnetic cavities

Electrical conductivity of one-dimensional (1d) disordered solids decays exponentially with their length, which is a celebrated manifestation of the localization phenomenon. Here, we study the modifications of localized conductivity induced by placement of 1d semiconductors inside of single-mode electromagnetic cavities, focusing on the regime of non-degenerate doping. We use the Green's function technique modified for the non-perturbative account of cavity excited states, and including both coherent electron-cavity effects (i.e. electron motion in the zero-point fluctuating field) and incoherent processes of photon emission upon tunneling. The energy spectrum of electron transmission in the cavity acquires Fano-type resonances associated with virtual photon emission, passage along the resonant level, and photon re-absorption. The quality factor of the Fano resonance depends on whether the intermediate state is coupled to the leads, and reaches its maximum when this state is localized deep in the disorder potential. Coupling to the cavity also elevates the energies of the shallow bound states, bringing them to the conduction band bottom. Such an effect leads to the enhancement of the low-temperature conductance.

cond-mat.mes-hall↗

arXiv2023

Ultimate sharpness of the tunneling resonance in vertical heterostructures

Heterostructures comprised of two two-dimensional electron systems (2DES) separated by a dielectric exhibit resonant tunneling when the band structures of both systems are aligned. It is commonly assumed that the height and width of the resonant peak in the tunneling current is determined by electron scattering and rotational misalignment of crystal structures of the 2DES. We identify two fundamental factors limiting the maximum height and steepness of the resonance: coupling to contacts and tunnel splitting of energy levels. The upper limit of the tunneling current is the number of electrons available for tunneling times half the tunnel coupling between the 2DES. As a result of a tradeoff between the contact-induced level broadening and contact resistance, the maximum current is only achievable when the coupling to contacts equals the tunnel level splitting. According to our model calculations, the limiting behavior can be observed in double-gated graphene/few-layer hexagonal boron nitride/graphene heterostructures.

cond-mat.mes-hall↗

arXiv2023

Refraction laws for two-dimensional plasmons

Despite numerous applications of two-dimensional plasmons for electromagnetic energy manipulation at the nanoscale, their quantitative refraction and reflection laws (analogs of Fresnel formulas in optics) have not yet been established. This fact can be traced down to the strong non-locality of equations governing the 2d plasmon propagation. Here, we tackle this difficulty by direct solution of plasmon scattering problem with Wiener-Hopf technique. We obtain the reflection and transmission coefficients for 2d plasmons at the discontinuity of 2d conductivity at arbitrary incidence angle, for both gated and non-gated 2d systems. At a certain incidence angle, the absolute reflectivity has a pronounced dip reaching zero for gated plasmons. The dip is associated with wave passage causing no dynamic charge accumulation at the boundary. For all incidence angles, the reflection has a non-trivial phase different from zero and $π$.

physics.optics↗

arXiv2022

Ultralow-noise terahertz detection by p-n junctions in gapped bilayer graphene

Graphene shows a strong promise for detection of terahertz (THz) radiation due to its high carrier mobility, compatibility with on-chip waveguides and transistors, and small heat capacitance. At the same time, weak reaction of graphene's physical properties on the detected radiation can be traced down to the absence of band gap. Here, we study the effect of electrically-induced band gap on THz detection in graphene bilayer with split-gate p-n junction. We show that gap induction leads to simultaneous increase in current and voltage responsivities. At operating temperatures of ~25 K, the responsivity at 20 meV band gap is from 3 to 20 times larger than that in the gapless state. The maximum voltage responsivity of our devices at 0.13 THz illumination exceeds 50 kV/W, while the noise equivalent power falls down to 36 fW/Hz^0.5. These values set new records for semiconductor-based cryogenic terahertz detectors, and pave the way for efficient and fast terahertz detection.

cond-mat.mes-hall↗

arXiv2021

Tunnel field-effect transistors for sensitive terahertz detection

The rectification of electromagnetic waves to direct currents is a crucial process for energy harvesting, beyond-5G wireless communications, ultra-fast science, and observational astronomy. As the radiation frequency is raised to the sub-terahertz (THz) domain, ac-to-dc conversion by conventional electronics becomes challenging and requires alternative rectification protocols. Here we address this challenge by tunnel field-effect transistors made of bilayer graphene (BLG). Taking advantage of BLG's electrically tunable band structure, we create a lateral tunnel junction and couple it to an antenna exposed to THz radiation. The incoming radiation is then down-converted by the tunnel junction nonlinearity, resulting in high-responsivity (> 4 kV/W) and low-noise (0.2 pW/$\sqrt{\mathrm{Hz}}$}) detection. We demonstrate how switching from intraband Ohmic to interband tunneling regime can raise detectors' responsivity by few orders of magnitude, in agreement with the developed theory. Our work demonstrates a potential application of tunnel transistors for THz detection and reveals BLG as a promising platform therefor.

cond-mat.mes-hall↗

arXiv2020

Feasibility of lasing in the GaAs Reststrahlen band with HgTe multiple quantum well laser diodes

Operation of semiconductor lasers in the 20--50 $μ$m wavelength range is hindered by strong non-radiative recombination in the interband laser diodes, and strong lattice absorption in GaAs-based quantum cascade structures. Here, we propose an electrically pumped laser diode based on multiple HgTe quantum wells with band structure engineered for Auger recombination suppression. Using a comprehensive model accounting for carrier drift and diffusion, electron and hole capture in quantum wells, Auger recombination, and heating effects, we show the feasibility of lasing at $λ= 26...30$ $μ$m at temperatures up to 90 K. The output power in the pulse can reach up to 8 mW for microsecond-duration pulses.

cond-mat.mes-hall↗

arXiv2019

Fundamental limits to far-infrared lasing in Auger-suppressed HgCdTe quantum wells

A challenge of bridging the terahertz gap with semiconductor lasers faces an inevitable problem of enhanced non-radiative Auger recombination with reduction of photon energy. We show that this problem can be mitigated in mercury-cadmium-telluride quantum wells (HgCdTe QWs) wherein the Auger process is suppressed due to formation of quasi-relativistic electron-hole dispersion imposing strong energy-momentum restrictions on recombining carriers. Such dispersion is formed upon interaction of topological states at the two QW interfaces. We characterize the lasing properties of HgCdTe QWs quantitatively by constructing a microscopic theory for recombination, absorption, and gain, and show the feasibility of lasing down to ~ 50 $μ$m at liquid nitrogen temperature with threshold currents two orders of magnitude lower than in existing lasers. Our findings comply with recent experimental data on stimulated far-infrared emission from HgCdTe QWs and show the directions toward achievement of maximum possible lasing wavelength.

cond-mat.mes-hall↗

arXiv2018

Auger recombination in Dirac materials: A tangle of many-body effects

The peculiar electron dispersion in Dirac materials makes lowest-order Auger processes prohibited or marginally prohibited by energy and momentum conservation laws. Thus, Auger recombination (AR) in these materials is very sensitive to many-body effects. We incorporate them at the level of the $GW$ approximation into the nonequilibrium Green's functions approach to AR and study the role of dynamic screening, spectrum broadening and renormalization in the case of weakly pumped undoped graphene. We find that incorrect treatment of many-body effects can lead to an order-of-magnitude error in the recombination rate. We show that the AR time weakly (sublinearly) depends on the background dielectric constant, which limits the possibility to control recombination by the choice of substrate. However, the AR time can be considerably prolonged by placing graphene under a metal gate or by introducing a bandgap. With carrier cooling taken into account, our results comply with experiments on photoexcited graphene.

cond-mat.mes-hall↗