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Kh. Yu. Rakhimov

Publications and source records attributed to Kh. Yu. Rakhimov.

14 recordsLinked to original sources
arXiv2025

Wave-packet dynamics in a graphene with periodic potentials

We use the Dirac continuum model to study the propagation of electronic wave packets in graphene with periodically arranged circular potential steps. The time propagation of the wave packets are calculated using the split-operator method for different size, height and separation of the barriers. The time propagation of the wave packets is calculated using the split-operator method for various barrier sizes, heights, and separations. We found that, despite the pronounced Klein tunneling effect in graphene, the presence of a lattice of defects significantly impacts the propagation properties of the wave packets. For example, depending on the height and size of the incident wave packet, the transmission probability can decrease by more than 20\%. The alteration of the polarity of the potential barriers also contributes to the transmission probabilities of the wave packet in graphene. The obtained results could provide valuable insights into the fundamental understanding of charge carrier dynamics in graphene-based nanodevices.

cond-mat.mes-hall↗
arXiv2020

Relativistic photoeffect for $s$ states in a central field

We study the photoionization of the $s$ states in the systems bound by sufficiently weak central fields $V(r)$ for the large photon energies corresponding to the relativistic photoelectrons. We demonstrate that the energy dependence of the photoionization cross section can be obtained without solving the wave equation. We show that the shape of the energy dependence of the cross section is determined by analytical properties of the binding potential $V(r)$. We find the cross sections for the potentials $V(r)$ which have singularities in the origin, on the real axis and in the complex plane.

hep-ph↗
arXiv2011

Electron loss of fast heavy projectiles in collision with neutral targets

The multiple electron loss of heavy projectiles in fast ion-atom collisions has been studied in the framework of the sudden perturbation approximation. Especially, a model is developed to calculate the cross sections for the loss of any number of electrons from the projectile ion, including the ionization of a single electron and up to the complete stripping of the projectile. For a given collision system, that is specified by the (type and charge state of the) projectile and target as well as the collision energy, in fact, the experimental cross sections for just three final states of the projectile are required by this model in order to predict the loss of any number, $N$, of electrons for the same collision system, or for any similar system that differs only in the energy or the initial charge state of the projectile ion. The model is simple and can be utilized for both, the projectile and target ionization, and without that large computer resources are requested. Detailed computation have been carried out for the multiple electron loss of Xe$^{18+}$ and U$^{6+,\, 10+,\, 28+}$ projectiles in collision with neutral Ar and Ne gas targets.

physics.atom-ph↗
arXiv2011

Electron loss of fast projectiles in the collisions with molecules

The single and multiple electron loss of fast highly charged projectiles in the collisions with neutral molecules are studied within the framework of a nonperturbative approach. The cross sections for single, double, and triple electron losses are calculated for the collision system $Fe^{q+}\to N_2$ ($q$=24, 25, 26) at the collision energies 10, 100, and 1000 MeV/u. The effects caused by the collision multiplicity and the orientation of the axis of target molecule are treated. It is shown that collision multiplicity effect leads to considerable differences for the cases of perpendicular and parallel orientations of the molecular axes with respect to the direction of the projectile motion, while for chaotic orientation such effect is negligible.

quant-ph↗
arXiv2011

Wave packet dynamics and valley filter in strained graphene

The time evolution of a wavepacket in strained graphene is studied within the tight-binding model and continuum model. The effect of an external magnetic field, as well as a strain-induced pseudo-magnetic field, on the wave packet trajectories and zitterbewegung are analyzed. Combining the effects of strain with those of an external magnetic field produces an effective magnetic field which is large in one of the Dirac cones, but can be practically zero in the other. We construct an efficient valley filter, where for a propagating incoming wave packet consisting of momenta around the K and K' Dirac points, the outgoing wave packet exhibits momenta in only one of these Dirac points, while the components of the packet that belong to the other Dirac point are reflected due to the Lorentz force. We also found that the zitterbewegung is permanent in time in the presence of either external or strain-induced magnetic fields, but when both the external and strain-induced magnetic fields are present, the zitterbewegung is transient in one of the Dirac cones, whereas in the other cone the wave packet exhibits permanent spatial oscillations.

cond-mat.mes-hall↗
arXiv2009

Spectra of heavy-light mesons at finite temperature

Spectra of heavy-light meson are studied using potential model and thermofield dynamics prescription. The mass spectra of different heavy-light mesons are calculated at different temperatures and compared with those at T=0. It is found that the binding mass of heavy-light meson decreases as temperature increases.

hep-ph↗
arXiv2006

Formation of ions by high energy photons

We calculate the electron energy spectrum of ionization by a high energy photon, accompanied by creation of electron-positron pair. The total cross section of the process is also obtained. The asymptotics of the cross section does not depend on the photon energies. At the photon energies exceeding a certain value $ω_0$ this appeares to to be the dominant mechanism of formation of the ions. The dependence of $ω_0$ on the value of nuclear charge is obtained. Our results are consistent with experimental data.

quant-ph↗
arXiv2006

Spectra of Quarkonia at Finite Temperature

Finite-temperature spectra of heavy quarkonia are calculated by combining potential model and thermofield dynamics formalisms. The mass spectra of the heavy quarkonia with various quark contents are calculated. It is found that binding mass of the quarkonium decreases as temperature increases.

hep-ph↗
arXiv2003

Quantum time ordering and degeneracy. II: Coherent population transfer between degenerate states

We find conditions required to achieve complete population transfer, via coherent population trapping, from an initial state to a designated final state at a designated time in a degenerate $n$-state atom, where transitions are caused by an external interaction. In systems with degenerate states there is no time ordering. Analytic expressions have been found for transition probabilities in a degenerate $n$-state atom interacting with a strong external field that gives a common time dependence to all of the transition matrix elements. Except for solving a simple $n^{th}$ order equation to determine eigenvalues of dressed states, the method is entirely analytic. These expressions may be used to control electron populations in degenerate $n$-state atoms. Examples are given for $n=2$ and $n=3$.

quant-ph↗
arXiv2003

Complete population transfer in a degenerate 3-level atom

We find conditions required to achieve complete population transfer, via coherent population trapping, from an initial state to a designated final state at a designated time in a degenerate 3-level atom, where transitions are caused by an external interaction. Complete population transfer from an initially occupied state 1 to a designated state 2 occurs under two conditions. First, there is a constraint on the ratios of the transition matrix elements of the external interaction. Second, there is a constraint on the action integral over the interaction, or "area", corresponding to the phase shift induced by the external interaction. Both conditions may be expressed in terms of simple odd integers.

quant-ph↗
arXiv2003

Complete population transfer in degenerate n-state atoms

We find a set of conditions to achieve complete population transfer, via coherent population trapping, from an initial state to a designated final state at a designated time in a degenerate n-state atom, where the transitions are caused by an external interaction.

quant-ph↗
arXiv1998

Inelastic Processes in the Collision of Relativistic Highly Charged Ions with Atoms

A general expression for the cross sections of inelastic collisions of fast (including relativistic) multicharged ions with atoms which is based on the genelazition of the eikonal approximation is derived. This expression is applicable for wide range of collision energy and has the standard nonrelativistic limit and in the ultrarelativistic limit coincides with the Baltz's exact solution ~\cite{art13} of the Dirac equation. As an application of the obtained result the following processes are calculated: the excitation and ionization cross sections of hydrogenlike atom; the single and double excitation and ionization of heliumlike atom; the multiply ionization of neon and argon atoms; the probability and cross section of K-vacancy production in the relativistic $U^{92+} - U^{91+}$ collision. The simple analytic formulae for the cross sections of inelastic collisions and the recurrence relations between the ionization cross sections of different multiplicities are also obtained. Comparison of our results with the experimental data and the results of other calculations are given.

physics.atom-ph↗