arXiv subjects

Miloud Mekkaoui

Publications and source records attributed to Miloud Mekkaoui.

30 records · Page 2Linked to original sources

arXiv2020

Confinement in Gapped Graphene with Magnetic Flux

We study the propagation of electrons in a circular quantum dot of gapped graphene subject to the magnetic flux $ϕ$. We present analytical expressions for the eigenstates, scattering coefficients, scattering efficiency and radial component of the reflected current. We identify different scattering regimes as a function of the physical parameters such as the incident electronic energy, potential barrier, radius of quantum dot, gap and $ϕ$. We choose two values of the flux $ϕ=1/2, 3/2$ and show that for low energy of the incident electron, the scattering resonances appear and the far-field scattered current presents distinct preferred scattering directions.

cond-mat.mes-hall↗

arXiv2020

Time-dependent Goos-Hänchen Shifts in Gapped Graphene

We study the Goos-Hänchen (GH) shifts for transmitted Dirac fermions in gapped graphene through a single barrier structure having a time periodic oscillating component. Our analysis shows that the GH shifts in transmission for central band $l=0$ and two first sidebands $l=\pm1$ change sign at the Dirac points $E=V+l\hbarω$. In particular the GH shifts inbtransmission exhibit enhanced peaks at each bound state associated with the single barrier when the incident angle is less than the critical angle associated with total reflection. Klein tunneling, reflected by perfect transmission at normal incidence, is also preserved in the presence of an oscillating barrier.

cond-mat.mes-hall↗

arXiv2019

Transmission in Graphene through Time-oscillating Linear Barrier

Transmission probabilities of Dirac fermions in graphene under linear barrier potential oscillating in time are investigated. Solving Dirac equation we end up with the solutions of the energy spectrum depending on several modes coming from the oscillations. These will be used to obtain a transfer matrix that allows to determine transmission amplitudes of all modes. Due to numerical difficulties in truncating the resulting coupled channel equations, we limit ourselves to low quantum channels, i.e. $l = 0, \pm1$, and study the three corresponding transmission probabilities.

cond-mat.mes-hall↗

arXiv2019

Effect of Magnetic Field on Goos-Hänchen Shifts in Gaped Graphene Triangular Barrier

We study the effect of a magnetic field on Goos-Hänchen shifts in gaped graphene subjected to a double triangular barrier. Solving the wave equation separately in each region composing our system and using the required boundary conditions, we then compute explicitly the transmission probability for scattered fermions. These wavefunctions are then used to derive the Goos-Hänchen shifts in terms of different physical parameters such as energy, electrostatic potential strength and magnetic field. Our numerical results show that the Goos-Hänchen shifts are affected by the presence of the magnetic field and depend on the geometrical structure of the triangular barrier.

cond-mat.mes-hall↗

arXiv2018

Goos-Hänchen Shifts in Graphene-Based Linear Barrier

Using the energy spectrum of a system made of graphene subjected to a linear barrier potential, we study the Goos-Hänshen shifts. The calculation is done by first determining the corresponding phase shifts via the transmission and reflection probabilities. Numerical analysis shows that the Goos-Hänshen shifts depend strongly on the incident energy, barrier height and width, and vary positively or negatively under suitable conditions.

cond-mat.mes-hall↗

arXiv2016

Tunneling of Graphene Massive Dirac Fermions through a Double Barrier

We study the tunneling of Dirac fermions in graphene through a double barrier potential allowing the carriers to have an effective mass inside the barrier as generated by a lattice miss-match with the boron nitride substrate. The consequences of this gap opening on the transmission are investigated. The realization of resonant tunneling conditions is also analyzed.

cond-mat.mes-hall↗

arXiv2016

Controllable Goos-Hänchen Shift in Graphene Triangular Double Barrier

We study the Goos-Hänchen shifts for Dirac fermions in graphene scattered by a triangular double barrier potential. The massless Dirac-like equation was used to describe the scattered fermions by such potential configuration. Our results show that the GHL shifts is affected by the geometrical structure of the double barrier. In particular the GHL shifts change sign at the transmission zero energies and exhibit enhanced peaks at each bound state associated with the double barrier when the incident angle is less than the critical angle associated with the total reflection.

cond-mat.mes-hall↗

arXiv2015

Transmission via Triangular Double Barrier and Magnetic Fields in Graphene

We study the transmission probability of Dirac fermions in graphene scattered by a triangular double barrier potential in the presence of an external magnetic field. Our system made of two triangular potential barrier regions separated by a well region characterized by an energy gap $G_p$. Solving our Dirac-like equation and matching the solutions at the boundaries we express our transmission and reflection coefficients in terms of transfer matrix. We show in particular that the transmission exhibits oscillation resonances that are manifestation of the Klein tunneling effect.

cond-mat.mes-hall↗

arXiv2015

Transmission and Goos-Hänchen like Shifts through a Graphene Double Barrier in an Inhomogeneous Magnetic Field

We studied the transport properties of electrons in graphene as they are scattered by a double barrier potential in the presence of an inhomogeneous magnetic field. We computed the transmission coefficient and Goos-Hänchen like shifts for our system and noticed that transmission is not allowed for certain range of energies. In particular, we found that, in contrast to the electrostatic barriers, the magnetic barriers are able to confine Dirac fermions. We also established some correlation between the electronic transmission properties of Dirac fermions with the Goos-Hänchen like shifts, as reflected in the numerical data.

cond-mat.mes-hall↗

arXiv2015

Transmissions in Graphene through Double Barriers and Periodic Potential

Transmission of Dirac fermions through a chip of graphene under the effect of magnetic field and a time vibrating double barrier with frequency $w$ is investigated. Quantum interference within the oscillating barrier has an important effect on quasi-particles tunneling. A combination of both a time dependent potential and a magnetic field generate physical states whose energy is double quantified by the pair of integers $(n, l)$ with high degeneracy. The large number of modes that exist in the energy spectrum presents a colossal difficulty in numerical computations. Thus we were obliged to make a truncation and limit ourselves to the central $(n = 0)$ and two adjacent side band ($n=\pm 1$).

cond-mat.mes-hall↗

arXiv2014

Goos-Hänchen like Shifts for Graphene Barrier in Constant Magnetic Field

We consider a system of Dirac fermions in graphene submitted to a constant perpendicular magnetic field and scattered by a barrier potential. We show that our system can be used to establish a link with quantum optics through the Goos-Hänchen shifts. This can be done by evaluating the corresponding transmission probability and shift phase. We obtain Goos-Hänchen like shifts in terms of different physical parameters such as energy, electrostatic potential strength and magnetic field. On the light of this relation, we discuss the obtained results and make comparison with literature.

cond-mat.mes-hall↗

arXiv2014

Tunneling of Massive Dirac Fermions in Graphene through Time-periodic Potential

The energy spectrum of graphene sheet with a single barrier structure having a time periodic oscillating height and subjected to magnetic field is analyzed. The corresponding transmission is studied as function of the obtained energy and the potential parameters. Quantum interference within the oscillating barrier has an important effect on quasiparticles tunneling. In particular the time-periodic electromagnetic field generates additional sidebands at energies ε+ l\hbar ω(l=0,\pm 1, \cdots) in the transmission probability originating from the photon absorption or emission within the oscillating barrier. Due to numerical difficulties in truncating the resulting coupled channel equations we limited ourselves to low quantum channels, i.e. l=0,\pm 1.

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