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We study the transmission of Dirac fermions in graphene through a tilted barrier potential in the presence of a laser field of frequency $\omega$. By using Floquet theory, we solve the Dirac equation and then obtain the energy spectrum. The boundary conditions together with the transfer matrix method allow us to determine the transmission probabilities corresponding to all energy bands $E+l\hbar\omega$ $(l=0,\pm1, \cdots)$. By limiting to the central band $l=0$ and the two first side bands $l=\pm 1$, we show that the transmissions are strongly affected by the laser field and barrier. Indeed, it is found that the Klein effect is still present, a variety of oscillations are inside the barrier, and there is essentially no transmission across all bands., Comment: 10 pages, 6 figures. Clarifications and references added. Version to appear in Ann. Phys. (Berlin)

We investigate electrons tunneling in AB bilayer graphene through a triple electrostatic barrier in the presence of a perpendicular magnetic field. By way of the transfer matrix method and using the continuity conditions at the different interfaces, transmission probability is determined. Additional resonances appear for two-band tunneling and at normal incidence, and their number is proportional to the value of $U_4$ in cases where $U_2U_4$, anti-Klein tunneling increases with $U_2$. The transmission probability exhibits an interesting oscillatory behavior when $U_3>U_2=U_4$ and $U_3 U_2=U_4$. In the four-band tunneling case, transmission decreases in $T^+_+$, $T^-_+$ and $T^-_-$ channels in comparison with the single barrier case. It does, however, increase for $T^+_-$ when compared to the single barrier case. Transmission is suppressed in the gap region when an interlayer bias is introduced. Our results are relevant for electron confinements in AB bilayer graphene and for the development of graphene-based transistors., Comment: 12 pages, 6 figures

We study the transport properties of Dirac fermions through gapped graphene through a magnetic barrier irradiated by a laser field oscillating in time. We use Floquet theory and the solution of Weber's differential equation to determine the energy spectrum corresponding to the three regions composing the system. The boundary conditions and the transfer matrix approach {are} employed to explicitly determine the transmission probabilities for multi-energy bands and the associated conductance. As an illustration, we focus only on the three first bands: the central band $T_0$ (zero photon exchange) and the two first side bands $T_{\pm1}$ (photon emission or absorption). It is found that the laser field activates the process of translation through photon exchange. Furthermore, we show that varying the incident angle and energy gap strongly affects the transmission process. The conductance increases when the number of electrons that cross the barrier increases, namely when there is a significant transmission., Comment: 12 pages, 7 figures

Whereas solar photovoltaic cells are promising for proper power production,their wide deployment is hampered by production costs, material availability and toxicity. One of these materials is CuO, which has great chemical stability as well as interesting physical properties, including a direct band gap, a high absorption coef cient, and p-type conductivity. These properties indicate CuO as an exciting semiconducting material to use an absorber layer in thin lms solar cells. For this speci c reason, this paper focuses on the synthesis of undoped and Ni-doped CuO thin lms by spray pyroly- sis process. Several techniques such as; X-ray diffraction (XRD), Raman spectroscopy, Scanning Electron Microscopy (SEM), Energy dispersive X-ray (EDX) and UV-Visible spectroscopy have been employed to characterize the synthesized samples. The XRD analysis indicated the formation of polycrystalline CuO thin lms and the average crystallite size was decreased from 35 to 20 nm for the samples with x = 0 to 8 at%, respectively. Furthermore, Raman spectroscopy also con rms the single-phase formation of CuO lms. The SEM images demonstrated that the incorporation of Ni in the CuO matrix improved the lms surface. The EDX analysis and the elemental mapping belay the homogeneous distribution of the elements. Moreover, UV-Visible spectroscopy has shown a signi cant expansion in optical energy band gap from 1.45 to 1.53 eV with an increase of Ni concentration. On the other hand, to investigate the impact of Ni-doped CuO on nanos- tructure Ni:CuO/ ZnO-NRs heterojunction solar cell performance, SCAPS-1D software is used. It has been found that, 8% Ni:CuO layer has been revealed as better for nanostructured solar cells. The results of this contribution will provide some vital guidelines for fabricating higher-ef ciency solar cells.

We solve the Dirac equation in three regions of graphene to get the solutions of the energy spectrum in connection to the strain, energy gap, and magnetic field. The Goos-H\"anchen shifts and group delay time will be obtained by applying the stationary phase approximation after the wave functions at the interfaces have been matched. Our results suggest that the group delay time is influenced by the presence of strain along the armchair and zigzag directions. We show that the gate voltage and strain have the ability to change the group delay from subluminality to superluminality. This may have significant uses in high-speed graphene-based nanoelectronics., Comment: 13 pages, 7 figures

The quantum entanglement of two connected harmonic oscillators via angular momentum yielding a magnetic coupling [Formula: see text] is discussed in this study. The corresponding Hamiltonian is diagonalized by using three canonical transformations, and then the stationary wave function is obtained. The Schmidt decomposition is used to explicitly determine the modes [Formula: see text], with [Formula: see text], [Formula: see text] and [Formula: see text] being two quantum numbers associated with the two oscillators. We summarize our findings by looking at the effects of anisotropy [Formula: see text], [Formula: see text], asymmetry [Formula: see text], and dynamics on entanglement. (i) With increasing [Formula: see text], the entanglement grows exceedingly large. (ii) The sensitivity to [Formula: see text] is determined by [Formula: see text] and [Formula: see text]. The physical parameters and quantum numbers play a great role in the periodic resuscitation of entanglement.

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., Comment: 10 pages, 10 figures

We investigate the effect of strain along armchair and zigzag directions on electrical transport in graphene through a magnetic barrier and a linearly polarized electromagnetic wave. In the context of Floquet theory, the eigenvalues and related eigenspinors are calculated analytically. The transmission probabilities are expressed as a function of different parameters using the transfer matrix approach and boundary conditions at two interfaces with current densities. We see that as the barrier width and incident energy change, the transmission via the center band oscillates less at zero strain. The transmission across the first sidebands begins at 0 and follows the pattern of a sinusoidal function that grows with increasing barrier width and becomes nearly linear for larger incident energy. When the strain magnitude is activated, the number of oscillations in all transmission channels drops marginally in the armchair direction but increases dramatically in the zigzag direction. The behavior of the total transmission is found to be comparable to that of the central band, with the exception that it exhibits a translation to the up. The suppression of Klein tunneling at normal incidence is another result seen in all strain settings., Comment: 12 pages, 5 figures. Clarifications and references added. Version to appear in Physica E

We study the intrinsic decoherence of coupled harmonic oscillators. The Milburn master equation is solved exactly, and the dynamics of virtual ground state excitations are investigated. The interaction of quantum correlations and virtual excitation was then studied. The following is a summary of our major findings. (i) The damped oscillatory profile of all three quantities is the same. (ii) Ultra-strong coupling combined with huge anisotropy values results in the reemergence of entanglement and steering. (iii) To sustain entanglement and steering, virtual excitations are required. (iv) The quantum correlations are amplified in the quantum synchronous regime. (v) Ultra-strong couplings cause inherent decoherence to be avoided., Comment: 11 pages, 4 figures

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. Solving our Dirac-like equation and matching the solutions at the boundaries allowed us to express our transmission and reflection coefficients in terms of transfer matrix. We show in particular that the transmission exhibits oscillation resonances that are manifestations of the Klein tunneling effect. The triangular barrier electrostatic field was found to play a key role in controlling the peak of tunneling resistance. However, it only slightly modifies the resonances at oblique incidence and leaves Klein paradox unaffected at normal incidence., Comment: 20 pages, 10 figures. arXiv admin note: substantial text overlap with arXiv:1511.06880

The conductance through single-layer graphene (SLG) and AA/AB-stacked bilayer graphene (BLG) junctions is obtained by taking into account band gap and bias voltage terms. First, we consider gapped SLG, while in between, they are connected into pristine BLG. For Fermi energy larger than the interlayer hopping, the conductance as a function of the bilayer region length $d$ reveals two different models of anti-resonances with the same period. As a function of the band gap, with AA-BLG stacking, the results show that the conductance has the same minima whatever the value of $d$, and for AB-BLG, $d$ remains relevant such that the system creates a global energy gap. Second, we consider pristine SLG, and in between, they are connected to gapped-biased BLG. We observe the appearance of peaks in the conductance profile with different periods and shapes, and also the presence of Klein tunneling with zero conductance in contrast to the first configuration. When $ d $ is less than 10, $G(E)$ vanishes and exhibits anti-Klein tunneling as a function of the Fermi energy $E$. We also investigate the conductance as a function of the bias. For AA-BLG, the results show antiresonances and diminish for a large value of the bias, independently of the bilayer region of length. In contrast, the conductance in AB-BLG has distinct characteristics in that it begins conducting with maxima for small $E$ and with minima for large $E$., Comment: 9 pages, 9 figures, two-column

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 $\Phi_i$. 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 $\Delta G$ oscillations., Comment: 8 pages, 10 figures, two columns

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 $\lambda$ and incident angle $\theta$ 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.

We investigate spin-dependent transmission in a curved graphene superlattice of $N$ cells where each one is made up of four regions. The first is concave, and the third is convex, two arcs of circles separated by a distance $d$ from flat graphene sheets. The tunneling analysis allows us to determine all transmission and reflection channels associated with our system. As a result, we show that the number of cells acts by decreasing the transmissions with the same spin. We predict a solid spin-filtering effect when $d$ and $N$ are sufficiently large. Finally, it is determined that the degree and duration of suppression of the transmissions with the same spin over a range of energy are controllable using $d$., Comment: 13 pages, 8 figures. Clarifications and references added. Version to appear in Phys. Scr

The Milburn dynamics of three nonresonant ultra-strongly coupled oscillators are resolved by using symplectic geometry. We look at the Milburn dynamics of virtual excitations and how they affect pairwise entanglement. It is found that the dynamics of excitations and entanglement experience similar profiles against time, physical parameters, and decoherence rate. Furthermore, we show that the extinction of excitations entails separability, which demonstrates the hierarchy between entanglement and virtual excitations. Additionally, we analyze the effects of physical parameters on the redistribution of virtual excitations among the three bi-partitions. As a result, we show the violation of the monogamy of excitations as in quantum discord. This implies that excitations can be considered as signatures of quantum correlations beyond entanglement. Besides, we emphasize that our treatment can be used to model coupled quantum circuits in real situations (with decoherence)., Comment: 13 pages, 7 figures. Clarifications and references added. Version to appear in Ann. Phys. (Berlin)

We investigate the transport properties of charge carriers in AB bilayer graphene through a triple electrostatic barrier. We calculate the transmission and reflection using the continuity conditions at the interfaces of the triple barrier together with the transfer matrix method. First, we consider the case where the energy is less than the interlayer coupling $\gamma_1$ and show that, at normal incidence, transmission is completely suppressed in the gap for a large barrier width while it appears in the gap for a small barrier width. For energies greater than $\gamma_1$, we show that in the absence of an interlayer potential difference, transmission is less than that of a single barrier, but in its presence, transmission in the gap region is suppressed, as opposed to a double barrier. It is found that one, two, or three gaps can be created depending on the number of interlayer potential differences applied. Resonance in the $T_-^+$ transmission channel is observed that is not seen in the single and double barrier cases. Finally, we compute the conductance and show that the number of peaks is greater than the double barrier case., Comment: 8 pages, 7 figures

The insertion of the band gap $\Delta$ in the rippled graphene superlattice leads to new outcomes, as demonstrated. The essential thing is the appearance of opposite-spin transmissions, which increase with $\Delta$ and vanish without it. Furthermore, compared to the $\Delta=0$ scenario, the duration of the suppression of the transmission with the same spin is longer, with many peaks. The maximum value of transmissions with the same spin declines and remains around unity. Furthermore, for particular energy values, a shift in the behavior of the transmission channels is found. As a result, we demonstrate that with $\Delta$, transmission filtering becomes crucial. Finally, as a result of the band gap, distinct variations in total conductance are discovered., Comment: 10 pages, 6 figures

We study transmission in a system consisting of a curved graphene surface as an arc (ripple) of circle connected to two flat graphene sheets on the left and right sides. We introduce a mass term in the curved part and study the effect of a generated band gap in spectrum on transport properties for spin-up/-down. The tunneling analysis allows us to find all transmission and reflections channels modeled by the band gap. This later acts by decreasing the transmissions with spin-up/-down but increasing with spin opposite, which exhibit some behaviors look like bell-shaped curve. We find resonances appearing in reflection with the same spin, thus backscattering with a spin-up/-down is not null in ripple. We observe huge spatial shifts for the total conduction in our model and the magnitudes of these shifts can be efficiently controlled by adjusting the band gap. This high order tunability of the tunneling effect can be used to design highly accurate devises based on graphene., 17 pages, 10 figures. Clarifications and references added

Using the circulant symmetry of a Hamiltonian describing three qubits, we realize the quantum Fourier transform. This symmetry allows us to construct a set of eigenvectors independently on the magnitude of physical parameters involved in the Hamiltonian and as a result, the entanglement will be maintained. The realization will be leaned on trapped ions and the gate implementation requires an adiabatic transition from each spin product state to Fourier modes. The fidelity was numerically calculated and the results show important values. Finally, we discuss the acceleration of the gate by using the counter-driving field., Comment: 21 pages, 7 figures. Clarifications and references added. Version to appear in JPA

We investigate transport properties through a rectangular potential barrier in AB-stacked bilayer graphene (AB-BLG) gapped by dielectric layers. Using the Dirac-like Hamiltonian with a transfer matrix approach we obtain transmission and reflection probabilities as well as the associated conductance. For two-band model and at normal incidence, we find extra resonances appearing in transmission compared to biased AB-BLG, which are Fabry-P\'erot resonance type. Now by taking into account the inter-layer bias, we show that both of transmission and anti-Klein tunneling are diminished. Regarding four band model, we find that the gap suppresses transmission in an energy range by showing some behaviors look like "Mexican hats". We examine the total conductance and show that it is affected by the gap compared to AA-stacked bilayer graphene. In addition, we find that the suppression in conductance is more important than that for biased AB-BLG., Comment: 9 pages, 2 column, 7 figures

We obtain the gauge invariant energy eigenvalues and degeneracies together with rotationally symmetric wavefunctions of a particle moving on 2D noncommutative plane subjected to homogeneous magnetic field $B$ and harmonic potential. This has been done by using the phase space coordinates transformation based on 2-parameter family of unitarily equivalent irreducible representations of the nilpotent Lie group $G_{NC}$. We find that the energy levels and states of the system are unique and hence, same goes to the degeneracies as well since they are heavily reliant on the applied $B$ and the noncommutativity $\theta $ of coordinates. Without $B$, we essentially have a noncommutative planar harmonic oscillator under generalized Bopp shift or Seiberg-Witten map. The degenerate energy levels can always be found if $\theta$ is proportional to the ratio between $\hbar$ and $m\omega$. For the scale $B\theta = \hbar$, the spectrum of energy is isomorphic to Landau problem in symmetric gauge and hence, each energy level is infinitely degenerate regardless of any values of $\theta$. Finally, if $0 < B\theta < \hbar$, $\theta$ has to also be proportional to the ratio between $\hbar$ and $m\omega$ for the degeneracy to occur. These proportionality parameters are evaluated and if they are not satisfied then we will have non-degenerate energy levels. Finally, the probability densities and effects of $B$ and $\theta$ on the system are properly shown for all cases., Comment: 23 pages, 9 figures

This paper surveys the quantum entanglement of two coupled harmonic oscillators via angular momentum generating a magnetic coupling $\omega_{c}$. The corresponding Hamiltonian is diagonalized by using three canonical transformations and then the stationary wave function is obtained. Based on the Schmidt decomposition, we explicitly determine the Schmidt modes $\lambda_{k}$ with $k\in\left\lbrace 0,1,\cdots,n+m\right\rbrace$, $n$ and $m$ being two quantum numbers associated to the two oscillators. By studying the effect of the anisotropy $ R=\omega_{1}^{2}/\omega_{2}^{2} $, $\omega_{c}$, asymmetry $ |n-m| $ and dynamics on the entanglement, we summarize our results as follows. $ (i)- $ The entanglement becomes very large with the increase of $ (n,m) $. $ (ii)- $ The sensistivity to $\omega_c$ depends on $ (n,m) $ and $R$. $ (iii)- $ The periodic revival of entanglement strongly depends on the physical parameters and quantum numbers., Comment: 12 pages, 4 figures

International audience; Electrochemical oxidation appears to be a practical technology for the decentralized treatment of wastewater in regions where sewer-based wastewater treatment is too expensive or otherwise impossible to construct and maintain. As of now, the control processes used by many systems rely principally on successive events that are time-dependent and come with some level of monitoring but little feedback into the system process. One reason is the high cost of sensors and automation systems used in industrial installations cannot easily translate into the household or public bathroom products for developing countries where capital expenditure is limited. As an answer to this challenge, we integrated a suite of inexpensive sensors (e.g., ORP, color, turbidity, voltage, current, water level, leakage) in and around the electrochemical treatment system and to a local computer (Raspberry Pi + Arduino) that can diagnose failure modes and send alerts to on-demand repair technicians and users. We also investigating the redesign of the sensors network to make it wireless at a low-cost in order to enjoy the benefits of wireless communications (e.g., monitoring flexibility, accessibility, and availability). The Wireless Sensor Network (WSN) will facilitate the installation of sensors as well as locating and managing failures.