arXiv subjects

Ahmed Bouhlal

Publications and source records attributed to Ahmed Bouhlal.

15 recordsLinked to original sources

arXiv2026

Comparative analysis of real experiments and digital (ICT) simulations regarding their impact on student learning

This study, conducted among more than 250 physics and chemistry teachers in Morocco, analyzes the impact of experimentation on student learning and attention in middle and high school. The results show that the majority of teachers favor digital simulations, except for simple experiments such as electrical circuits. This choice is linked to material constraints, class size, and safety requirements. Simulations are perceived as practical and flexible, allowing experiments to be repeated or slowed down to facilitate understanding. However, teachers emphasize the need for specific ICT training in order to better integrate these tools into their practices. The most effective strategy identified is based on a hybrid approach: using simulations to explain abstract phenomena and real experiments to develop experimental skills, methodological rigor, and critical thinking. This complementary approach appears to be a promising solution for enriching science education and overcoming the constraints encountered in schools.

physics.ed-ph↗

arXiv2025

Effect of laser field and magnetic flux on scattering in graphene quantum dots

We show how Dirac electrons interact with a graphene quantum dots (GQDs) when exposed to both a magnetic flux and circularly polarized light. After obtaining the solutions of the energy spectrum, we compute the scattering coefficients. These allow us to show how efficiently the electrons diffuse and how their probability density is distributed in space. Our results show that light polarization is key in controlling electron scattering. It affects electron localization near the GQDs and the strength of the scattering coefficients. We also investigate how light intensity and magnetic flux affect the formation of quasi-bound states. In addition, the electrostatic potential reduces the density of scattering states and fine-tunes the interaction between electrons and the quantum dot. This research improves our understanding of electron behavior in graphene nanostructures and suggests new ways to control electronic states at the quantum level.

cond-mat.mes-hall↗

arXiv2025

Electron trapping via magnetic and laser fields in gapped graphene quantum dots

We study electron scattering in graphene quantum dots (GQDs) under the combined influence of a magnetic field, an energy gap, and circularly polarized laser irradiation. Using the Floquet approach and the Dirac equation, we derive the energy spectrum solutions. The scattering coefficients are calculated explicitly by matching the eigenspinors at the GQD interfaces, revealing a dependence on several physical parameters. In addition, we compute the scattering efficiency, the electron density distribution, and the lifetime of the quasi-bound states. Our numerical results show that the presence of an energy gap and circularly polarized laser irradiation enhances the localization of the electron density within the GQDs, leading to an increase in the lifetime of the quasi-bound states. In particular, the intensity and polarization of the light influence the scattering process, allowing the manipulation of the electron confinement state. These results highlight the importance of combining magnetic fields and polarized light to control electronic transport in graphene nanostructures.

cond-mat.mes-hall↗

arXiv2024

Influence of Aharonov-Bohm flux and dual gaps on electron scattering in graphene quantum dots

We show how the Aharonov-Bohm flux (AB) $ϕ_i$ and the dual gaps $(Δ_1, Δ_2)$ can affect the electron scattering in graphene quantum dots (GQDs) of radius $r_0$ in the presence of an electrostatic potential $V$. After obtaining the solutions of the energy spectrum, we explicitly determine the radial component of the reflected current $J_r^r$, the square modulus of the scattering coefficients $|c_m|^2$, and the scattering efficiency $Q$. Different scattering regimes are identified based on physical parameters such as incident energy $E$, $V$, $r_0$, dual gaps, and $ϕ_i$. In particular, we show that lower values of $E$ are associated with larger amplitudes of $Q$. Furthermore, it is found that $Q$ exhibits a damped oscillatory behavior with increasing the AB flux. In addition, increasing the external gap $Δ_1$ resulted in higher values of $Q$. By increasing $ϕ_i$, we show that the oscillations in $|c_m|^2$ disappear for larger values of $r_0$ and are replaced by prominent peaks at certain values of $E$ and angular momentum $m$. Finally, we show that $J_{r}^r$ displays periodic oscillations of constant amplitude, which are affected by the AB flux.

cond-mat.mes-hall↗

arXiv2024

Aharonov-Bohm flux and dual gaps effects on energy levels in graphene magnetic quantum dots

We address the question of how the Aharonov-Bohm flux $Φ_{AB}$ can affect the energy levels of graphene magnetic quantum dots (GMQDs) of radius $R$. To answer this question, we consider GMQDs induced by a magnetic field $B$ and subjected to two different gaps - an internal gap $Δ_1$ and an external gap $Δ_2$. After determining the eigenspinors and ensuring continuity at the boundary of the GMQDs, we formulate an analytical equation describing the corresponding energy levels. Our results show that the energy levels can exhibit either a symmetric or an asymmetric behavior depending on the valleys $K$ and $K'$ together with the quantum angular momentum $m$. In addition, we find that $Φ_{AB}$ causes an increase in the band gap width when $Δ_1$ is present inside the GMQDs. This effect is less significant when a gap is present outside, resulting in a longer lifetime of the confined electronic states. Further increases in $Φ_{AB}$ reduce the number of levels between the conduction and valence bands, thereby increasing the band gap. These results demonstrate that the electronic properties of graphene can be tuned by the presence of the AB flux, offering the potential to control the behavior of graphene-based quantum devices.

cond-mat.mes-hall↗

arXiv2024

Boosting energy levels in graphene magnetic quantum dots through magnetic flux and inhomogeneous gap

We study the effects of a magnetic flux and an inhomogeneous gap on the energy spectrum of graphene magnetic quantum dots (GMQDs). By considering the Dirac equation in the infinite mass framework, we can analytically obtain eigenspinor expressions. By applying boundary conditions, we obtain an energy spectrum equation in terms of system parameters such as radius, magnetic field, energy, flux, and gap. In the infinite limit, we recover Landau levels for graphene in a magnetic field. We show that the energy spectrum increases significantly in the presence of flux and a gap inside the GMQDs, which prolongs the lifetime of the trapped electron states. We show that higher flux also produces new Landau levels of negative angular momentum. Meanwhile, we find that the gap increases the separation between the electron and hole energy bands. As shown in the radial probability analysis, flux and gap emerge as influential factors in controlling electron mobility, affecting confinement, and prolonging the presence of quasi-bound states.

cond-mat.mes-hall↗

arXiv2024

Electrons trapped in graphene magnetic quantum dots with mass term

Owing to the Klein tunneling phenomenon, the permanent confinement or localization of electrons within a graphene quantum dot is unattainable. Nonetheless, a constant magnetic field can transiently ensnare an electron within the quantum dot, giving rise to what are known as quasi-bound states characterized by finite lifetimes. To prolong the retention of electrons within the quantum dot, we introduce a mass term into the Hamiltonian, thereby inducing an energy gap. We resolve the Dirac equation to ascertain the eigenspinors, and by ensuring their continuity at the boundaries, we investigate the scattering behavior. Our findings indicate that the presence of an energy gap can extend the lifetimes of these quasi-bound states within the quantum dot. In particular, we demonstrate that even in the absence of a magnetic field, the scattering efficiency attains significant levels when the energy gap gets closed to the incident energy of an electron traversing the quantum dot. It is found that an augmentation in the electron density within the quantum dot results in an enhancement of the electron-trapping time.

cond-mat.mes-hall↗

arXiv2024

Effects of AB-flux and gap on magnetic graphene quantum dots

We consider magnetic graphene quantum dots (MGQDs) and study the impact of the Aharonov-Bohm (AB) flux and gap on the scattering process of electrons. Our emphasis is on the finite lifetimes of quasi-bound states arising from the interaction between electrons and the magnetic field within the dot. Initially, we calculate the scattering coefficients, scattering efficiency, and probability density by ensuring the continuity of eigenspinors at the boundary of MGQD. The results indicate that as the gap increases, the quasi-bound states reach higher maxima. We show that an increase in AB-flux leads to a generation of quasi-bound states requiring less magnetic field, and the scattering efficiency starts to take non-zero values at smaller MGQD sizes. The analysis of probability density shows that the quasi-bound states, corresponding to non-resonantly excited scattering modes, exhibit a significant improvement in the concentrated density at MGQD. The improvement is a result of reducing the diffraction phenomenon and suppressing the Klein effect through an increase in AB-flux and gap. This increases the probability of retaining the electron for a longer period of time.

cond-mat.mes-hall↗

arXiv2023

Energy levels of gapped graphene quantum dots in external fields

We investigate the energy levels of fermions within a circular graphene quantum dot (GQD) subjected to external magnetic and Aharonov-Bohm fields. Solving the eigenvalue equation for two distinct regions allows us to determine the eigenspinors for the valleys $K$ and $K^\prime$. By establishing the continuity of eigenspinors at the GQD interface, we derive an equation that reveals the reliance of energy levels on external physical parameters. Our observations suggest that the symmetry of energy levels hinges on the selected physical parameters. We observe that at low magnetic fields, the energy levels display degeneracy, which diminishes as the field strength increases, coinciding with the convergence of energy levels toward the Landau levels. We illustrate that the introduction of a magnetic flux into the GQD leads to the creation of an energy gap, extending the trapping time of electrons without perturbing the system. Conversely, the addition of gap energy widens the band gap, disrupting the system's symmetry by introducing new energy levels.

cond-mat.mes-hall↗

arXiv2023

Electron trapping in graphene quantum dots with magnetic flux

It is known that the appearance of Klein tunneling in graphene makes it hard to keep or localize electrons in a graphene-based quantum dot (GQD). However, a magnetic field can be used to temporarily confine an electron that is traveling into a GQD. The electronic states investigated here are resonances with a finite trapping time, also referred to as quasi-bound states. By subjecting the GDQ to a magnetic flux, we study the scattering phenomenon and the Aharonov-Bohm effect on the lifetime of quasi-bound states existing in a GQD. We demonstrate that the trapping time increases with the magnetic flux sustaining the trapped states for a long time even after the flux is turned off. Furthermore, we discover that the probability density within the GQD is also clearly improved. We demonstrate that the trapping time of an electron inside a GQD can be successfully extended by adjusting the magnetic flux parameters.

cond-mat.mes-hall↗

arXiv2022

Zero-energy states in graphene quantum dot with wedge disclination

We investigate the effects of wedge disclination on charge carriers in circular graphene quantum dots subjected to a magnetic flux. Using the asymptotic solutions of the energy spectrum for large arguments, we approximate the scattering matrix elements, and then study the density of states. It is found that the density of states shows several resonance peaks under various conditions. In particular, it is shown that the wedge disclination is able to change the amplitude, width, and positions of resonance peaks.

cond-mat.mes-hall↗

arXiv2022

Tunneling phase diagrams in anisotropic Multi-Weyl semimetals

Motivated by the exciting prediction of Multi-Weyl topological semimetals that are stabilized by point group symmetries [Phys. Rev. Lett. 108 (2012) 266802], we study tunneling phenomena for a class of anisotropic Multi-Weyl semimetals. We find that a distant detector for different ranges of an anisotropy parameter $λ$ and incident angle $θ$ will measure a different number of propagating transmitted modes. We present these findings in terms of phase diagrams that is valid for an incoming wave with fixed wavenumber $k$--energy is not fixed. To gain a deeper understanding of this phenomenon we then focus on the simplest case of an anisotropic quadratic Weyl-semimetal and analyze tunneling coefficients analytically and numerically to confirm the observations from the phase diagram. Our results show non-analytical behavior, which is the hallmark of a phase transition. This serves as a motivation to make a formal analogy with phase transitions that are known from statistical mechanics. Specifically, we argue that the long distance limit in our tunneling problem takes the place of the thermodynamic limit in statistical mechanics. More precisely, find a direct formal connection to the recently developed formalism for dynamical phase transitions [Reports on Progress in Physics 81 (5) (2018) 054001]. We propose that this analogy to phase transitions can help classify transport properties in exotic semimetals.

cond-mat.mes-hall↗

arXiv2022

Quantum tunneling in graphene Corbino disk in a solenoid magnetic potential with wedge disclination

We investigate the wedge disclination effect on quantum tunneling of a Corbino disk in gapped-graphene of inner $R_1$ and outer $R_2$ radii in the presence of magnetic flux $Φ_i$. We solve Dirac equation for different regions and obtain the solutions of energy spectrum in terms of Hankel functions. The asymptotic behaviors for large arguments allow us to determine the transmission, Fano factor and conductance. We establish the case where the crystal symmetry is modified locally by replacing a hexagon by pentagon, square, heptagon or octagon. We show that the wedge disclination $n$ modifies the amplitude of transmission oscillations. We find that the period of Fano factor oscillations is of the Aharonov-Bohm type, which strongly depends on $n$ where intense peaks are observed. As another result, $n$ changes the minimum and period of conductance oscillations of the Aharonov-Bohm type. We show that $n$ minimizes the effect of resonance and decreases the amplitude of conductance magnitude $ΔG$ oscillations.

cond-mat.mes-hall↗

arXiv2021

Tunneling in an anisotropic cubic Dirac semi-metal

Motivated by a recent first principles prediction of an anisotropic cubic Dirac semi-metal in a real material Tl(TeMo)$_3$, we study the behavior of electrons tunneling through a potential barrier in such systems. To clearly investigate effects from different contributions to the Hamiltonian we study the model in various limits. First, in the limit of a very thin material where the linearly dispersive $z$-direction is frozen out at zero momentum and the dispersion in the $x$-$y$ plane is rotationally symmetric. In this limit we find a Klein tunneling reminiscent of what is observed in single layer graphene and linearly dispersive Dirac semi-metals. Second, an increase in thickness of the material leads to the possibility of a non-zero momentum eigenvalue $k_z$ that acts as an effective mass term in the Hamiltonian. We find that these lead to a suppression of Klein tunneling. Third, the inclusion of an anisotropy parameter $λ\neq 1$ leads to a breaking of rotational invariance. Furthermore, we observed that for different values of incident angle $θ$ and anisotropy parameter $λ$ the Hamiltonian supports different numbers of modes propagating to infinity. We display this effect in form of a diagram that is similar to a phase diagram of a distant detector. Fourth, we consider coexistence of both anisotropy and non-zero $k_z$ but do not find any effect that is unique to the interplay between non-zero momentum $k_z$ and anisotropy parameter $λ$. Last, we studied the case of a barrier that was placed in the linearly dispersive direction and found Klein tunneling $T-1\propto θ^6+\mathcal{O}(θ^8)$ that is enhanced when compared to the Klein tunneling in linear Dirac semi-metals or graphene where $T-1\propto θ^2+\mathcal{O}(θ^4)$.

cond-mat.mes-hall↗

arXiv2020

Density of States Analysis of Electrostatic Confinement in Gapped Graphene

We investigate the electrostatic confinement of charge carriers in a gapped graphene quantum dot in the presence of a magnetic flux. The circular quantum dot is defined by an electrostatic gate potential delimited in an infinite graphene sheet which is then connected to a two terminal setup. Considering different regions composing our system, we explicitly determine the solutions of the energy spectrum in terms of Hankel functions. Using the scattering matrix together with the asymptotic behavior of the Hankel functions for large arguments, we calculate the density of states and show that it has an oscillatory behavior with the appearance of resonant peaks. It is found that the energy gap can controls the amplitude and width of these resonances and affect their location in the density of states profile.

cond-mat.mes-hall↗