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Hocine Bahlouli

Publications and source records attributed to Hocine Bahlouli.

At least 19 recordsLinked to original sources
arXiv2026

Fingerprints of an Imbert-Fedorov-like effect in the tunneling transmission of Rarita-Schwinger semi-metals

We study tunneling through a square barrier in a rotationally symmetric Rarita-Schwinger semi-metal and identify fingerprints of an Imbert-Fedorov-like effect in the tunneling transmission. The problem is intrinsically multichannel at all energies because there exist two propagating sectors with spin projections $m=1/2$ and $m=3/2$. We derive the transmission amplitudes analytically and compare the single-channel and coherent mixed-incidence cases in the two channels. Interestingly, we observe that tunneling at high energy shows a bias towards scattering into spin projection $3/2$ contributions. For single-channel injection, we find that the transmission remains symmetric under a mirror transformation of the incident angle. In contrast, for the coherent superposition, we find a directional asymmetry in the transmission probability $T(k_y)\neq T(-k_y)$. Importantly, this effect does not originate from an anisotropy of the dispersion. Instead, it arises from the phase structure of the multicomponent scattering states. The two spin projection sectors exhibit different scattering and barrier-propagation phases, which enter as interference terms when both channels appear as a coherent superposition. This interference term is identified as the cause of the broken mirror symmetry. We therefore discover an analog of the Imbert-Fedorov effect, at the level of interface-induced phase differences between internal wave components. Our result demonstrates that asymmetric tunneling can already occur in transport experiments, even in an idealized, isotropic multiband system, and should therefore not be automatically attributed solely to explicit band anisotropy.

cond-mat.mes-hall↗
arXiv2026

Driven Vortex Motion in Periodic Channel Potential Embedded in Superconducting Films

In this paper, we investigate vortex dynamics in periodically width-modulated superconducting channels by numerically solving the time-dependent Ginzburg-Landau (TDGL) equations. The channels are designed with sinusoidally varying widths characterized by their average width and modulation amplitude. The motion of driven vortices generates an oscillatory electric field with a fundamental frequency, $f_0$, set by the channel periodicity, together with higher-order harmonics. In contrast to the situation of vortex lattice dynamics in a periodic pinning landscape of circular holes considered by Al Luhaibi et al. [1], we show that the harmonic content of the generated electric field can be effectively controlled through the channel geometry. In particular, appropriately engineered channel profiles strongly suppress higher-order harmonics, yielding an electric-field response that closely approaches a pure sinusoidal waveform. These results demonstrate that geometric modulation offers a viable route to engineering low-harmonicity microwave signals in superconducting devices and may enable cryogenic on-chip waveform generators for controlling superconducting qubits. Such devices could provide a useful building block for scalable transmon-based quantum computing architectures.

cond-mat.supr-con↗
arXiv2026

Analytical Treatment of Noise-Suppressed Klein Tunneling in Graphene with Possible Implications for Quantum-Dot Qubits

We study quantum tunneling through a potential barrier whose height fluctuates in time and is modeled by Gaussian white noise. We map the stochastic dynamics onto an equivalent time-independent Lindblad equation for the density matrix, allowing fully analytical solutions. For Schrödinger particles, noise introduces dissipation that suppresses Fabry-Pérot oscillations and yields an exponentially decaying transmission. Applying the same formalism to graphene, we demonstrate that noise induces a complex longitudinal wavevector within the barrier, leading to a strong suppression of transmission and Klein tunneling, even at normal incidence. Our approach promises improved control over Klein tunneling. These results demonstrate that noisy barriers can act as tunable dissipative elements, offering a pathway to enhanced control of electron transport in graphene-based devices. We also briefly discuss how our results could guide the design of graphene quantum dots for potential use in spin qubit devices.

cond-mat.mes-hall↗
arXiv2026

Gate-tunable spin-valley transport via carrier velocity in monolayer WSe$_2$

We theoretically investigate spin- and valley-resolved quantum transport in monolayer tungsten diselenide (WSe$_2$) described by an effective massive Dirac Hamiltonian. Particular attention is devoted to a finite barrier region characterized by simultaneously modulated Fermi velocity and scalar potential. The barrier velocity $v_2$ is related to the external velocity $v_1$ through a velocity ratio $ξ=v_2/v_1$, motivated by an optical analogy with the Snell-Descartes law. The exact refraction condition depends on the full spin- and valley-resolved dispersion, and the simple ratio $ξ=v_2/v_1$ is recovered only in the massless, symmetric limit. The interplay of intrinsic spin-orbit coupling in the conduction and valence bands, quantified by $λ_c$ and $λ_v$, with spin- and valley-dependent Zeeman fields, $M_s$ and $M_v$, gives rise to substantial changes in the quasiparticle dispersion, leading to pronounced modifications of the transport characteristics. By solving the Dirac equation and enforcing current-conserving matching conditions at the interfaces, we compute the spin- and valley-dependent transmission probability and conductance. Our results demonstrate that the barrier velocity, scalar potential, incidence angle, incident energy, and barrier width serve as effective control parameters for transport, giving rise to strong anisotropy and resonant tunneling features. Furthermore, we show that both the magnitude and orientation of spin- and valley-polarized currents can be continuously tuned via velocity and potential modulation. These findings establish combined velocity and potential engineering as a powerful theoretical framework for controlling spin-valley physics in two-dimensional transition-metal dichalcogenides.

cond-mat.mes-hall↗
arXiv2026

Magnon bandstructure and topology in a periodically deformed Kagome lattice with DM interaction

We study the band structure and topology of magnons for a Heisenberg model with DM interaction on a deformed Kagome lattice. For simplicity, we focus on a periodically deformed lattice with hexagonal symmetry and an enlarged unit cell. This enlarged unit cell gives rise to a richer band structure than in the undeformed case. Analyzing band topology, there is a distinction between the topologically trivial case with anti-ferromagnetic coupling and the topologically rich case with ferromagnetic coupling. In the anti-ferromagnetic case, a spin-space symmetry, also present in the classical ground state, enforces these topologically trivial states. In the ferromagnetic case, this symmetry is spontaneously broken by the classical ground state. Consequently, the band structure also hosts rich topological features. Specifically, we observe many topological transitions and bands with Chern numbers ranging from $+2$ to $-2$, which makes the system richer than in the undeformed case. This emergent rich topological structure demonstrates that deformed magnets can host new and exciting physics.

cond-mat.str-el↗
arXiv2026

Field-tunable spin-valley transport in monolayer MoS$_2$

We study field-controlled spin-valley transport in monolayer MoS$_2$ through a single electrostatic barrier and a uniform off-resonant elliptically polarized irradiation. Starting from the massive Dirac Hamiltonian with intrinsic spin-orbit coupling, we use a high-frequency Floquet expansion to obtain an effective static model with a laser-renormalized mass (gap) term. We solve the scattering problem by spinor matching and derive the exact analytic expression for the transmission. The numerical results show that the drive tunes both the spin-valley-dependent propagation threshold inside the barrier and the Fabry-Pérot phase, creating controllable pass/stop bands. By varying both the laser intensity (amplitude) and the polarization shape, we show that the same junction can be switched between broadband valley filtering and resonance-selective operation, and the valley contrast remains visible in the Landauer conductance. Our findings establish an efficient route for realizing optically reconfigurable valleytronic and spintronic functionalities in MoS$_2$.

cond-mat.mes-hall↗
arXiv2026

Band Structure and topology of a periodically deformed Kitaev honeycomb model

Motivated by the growing interest in spin liquids and topological phases, as well as the rise of deformation engineering, we study the combined effects of deformation and magnetic fields on the honeycomb Kitaev model. The Kitaev model, as one of the prototypical and exactly solvable spin liquid-hosting models, serves as a simple platform that demonstrates the rich physics one can expect at the intersection of deformation physics and quantum spin liquids. Our work builds on a simplified solution to the undeformed base model that we present. This simplified solution allows for a straightforward extension of our analysis to the deformed case. After incorporating periodic deformations into the Kitaev model (chosen for its similarity to moiré physics), we investigate the effects of a hexagonally symmetric deformation on the band structure. We find that deformation leads to a smaller Brillouin zone with new band gaps at the edges, indicating the potential for topological transitions. Finally, we introduce a magnetic field to break time-reversal symmetry and thereby allow for non-trivial topology. We find that, under specific parameter conditions, the magnetic field leads to multiple band-gap closings and openings. An investigation into topological properties reveals nontrivial Chern numbers and a plethora of topological transitions. Our results suggest possible thermal Hall or Nernst-type responses. We also suggest a potential bulk measurement approach for he Chern numbers and possible path to physical realization. Most importantly, our results serve as a demonstration of the rich phenomenology that can arise due to the interplay between deformation and spin-liquid physics.

cond-mat.str-el↗
arXiv2026

Tunable Goos--Hänchen shifts and group delay time in single-barrier silicene

We investigate the Goos--Hänchen (GH) shifts and group delay time of Dirac fermions traversing a rectangular electrostatic potential barrier in silicene. By analyzing their dependence on the incident angle, barrier height, barrier width, and incident energy, we demonstrate that the GH shifts exhibit pronounced oscillations arising from quantum interference within the barrier region. The amplitude and number of oscillation peaks increase with increasing energy, barrier width, and incidence angle, resulting in enhanced lateral beam displacement. Meanwhile, the group delay time exhibits resonant features associated with the formation of quasi-bound states, increasing with barrier width, energy, and incidence angle, while decreasing with increasing barrier height. These results clarify how barrier-induced quantum interference controls both the lateral and temporal dynamics of Dirac fermions in silicene, highlighting the potential role of electrostatic barriers in enabling tunable transport in two-dimensional Dirac materials.

cond-mat.mes-hall↗
arXiv2025

Light induced transitions of valley Chern numbers and flat bands in a non-twisted moire graphene-hexagonal boron nitride superlattice

Motivated by the rich topology and interesting quasi-band structure of twisted moire materials subjected to light, we study a non-twisted moire material under the influence of light. Our work is in part motivated by a desire to find an easier-to-synthesize platform that can help experimentally elucidate the interesting physics of moiré materials coupled to light. Similar to twisted moire materials, we uncover rich topology and interesting band flattening effects, which we summarize in relevant plots such as a topological phase diagram. Our work demonstrates that much of the interesting phenomenology of twisted moire materials under the influence of electromagnetic waves seems to be generically present even in more experimentally accessible untwisted moire platforms, which remain highly tunable by light.

cond-mat.mes-hall↗
arXiv2025

Effective K valley Hamiltonian for TMD bilayers under pressure and application to twisted bilayers with pressure-induced topological phase transitions

Motivated by recent studies on topologically non-trivial moiré bands in twisted bilayer transition metal dichalcogenides (TMDs), we study MoTe$_2$ bilayer systems subject to pressure, which is applied perpendicular to the material surface. We start our investigation by first considering an untwisted bilayer system with an arbitrary relative shift between layers; a symmetry analysis for this case permits us to obtain a simplified effective low-energy Hamiltonian valid near the important $\mathbf{K}$ valley region of the Brillouin zone. Ab initio density functional theory (DFT) was then employed to obtain relaxed geometric structures for pressures within the range of 0.0 - 3.5 GPa and corresponding band structures. The DFT data were then fitted to the low-energy Hamiltonian to obtain a pressure-dependent Hamiltonian. We then apply our model to a twisted system by treating the twist as a position-dependent shift between layers - here, we assume rigid layers, which is a crucial simplification. In summary, this approach allowed us to obtain the explicit analytical expressions for a Hamiltonian that describes a twisted MoTe\textsubscript{2} bilayer under pressure. Our Hamiltonian then permitted us to study the impact of pressure on the band topology of the twisted system. As a result, we identified many pressure-induced topological phase transitions as indicated by changes in valley Chern numbers. Moreover, we found that pressure could be employed to flatten bands in some of the cases we considered.

cond-mat.mes-hall↗
arXiv2025

Effect of magnetic field and light on energy levels of (1+3+1) chirally twisted multilayer graphene system

We study the Hofstadter butterfly spectrum in (1+3+1) chirally twisted multilayer graphene (CTMLG) subject to perpendicular magnetic field and light with different polarizations. We focus on the interplay between twist angles and light-induced effects. In equilibrium, we examine symmetric ($θ_1 = θ_2$) and asymmetric ($θ_1 \neq θ_2$) configurations. Our results show that asymmetric configurations cause distinct effects in the electronic energy spectrum. However, the unique symmetry of the system ensures that the spectra remain identical when the twist angles are interchanged. This highlights the role of interlayer coupling in shaping the electronic structure of CTMLG. We then explored the effects of external periodic perturbations, such as circularly polarized light (CPL) and waveguide-generated linearly polarized light (WGL). CPL breaks chiral symmetry, creating a gap that distorts the Hofstadter spectrum. These distortions are more pronounced for asymmetric twist configurations. In contrast, WGL preserves chiral symmetry and has a tunable, non-monotonic effect on the bandwidth. This makes WGL a reliable tool for engineering electronic properties. These results demonstrate how (1+3+1)-CTMLG combines the effects of light-matter interactions with moiré physics. This allows accurate control of the electronic properties and fractal spectra by adjusting external fields and twist angles.

cond-mat.mes-hall↗
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↗
arXiv2024

Controlling Goos-Hänchen shifts in phosphorene via barrier and well

We study the effect of the double potentials (barrier, well) on the Goos-Hänchen (GH) shifts in phosphorene. We determine the solutions of the energy spectrum associated with the five regions that make up our system. By studying the phase shifts, we find that the GH shifts are highly sensitive to the incident energy, the $y$ directional wave vector, the potential heights and widths. To validate our findings, we perform a numerical analysis of the GH shifts as a function of the transmission probability under various conditions. In particular, we observe a consistent pattern in which a positive peak in the GH shift is always followed by a negative valley, a behavior evident at all potential height values. Notably, the energies at which the GH shift changes sign coincide exactly with the points at which transmission drops to zero. In particular, the transmission resonances that occur just before and just after the transmission gap region are strongly correlated with the points at which the GH shift changes sign. This study advances our understanding of how the double potential influences the GH shift behaviors in phosphorene. The ability to fine-tune the GH shifts by changing system parameters suggests potential applications in optical and electronic devices using this two-dimensional material.

cond-mat.mes-hall↗
arXiv2024

Semiclassical perspective on Landau levels and Hall conductivity in an anisotropic Cubic Dirac Semi-Metal and the peculiar case of star-shaped classical orbits

We study an anisotropic cubic Dirac semi-metal subjected to a constant magnetic field. In the case of an isotropic dispersion in the $x$-$y$ plane, with parameters $v_{x}=v_{y}$, it is possible to find exact Landau levels, indexed by the quantum number $n$, using the typical ladder operator approach. Interestingly, we find that the lowest energy level (the zero energy state in the case $k_z=0$) has a degeneracy that is three times that of other states. This degeneracy manifests in the Hall conductivity as a step at zero chemical potential that is 3/2 the size of other steps. Moreover, as $n\to\infty$ we find energies $E_n\propto n^{3/2}$, which means the $n$-th step as a function of chemical potential roughly occurs at a value $μ\propto n^{3/2}$. We propose that these exciting features could be used to identify cubic Dirac semi-metals experimentally. Subsequently, we analyze the anisotropic case $v_{y}=λv_{x}$ with $λ\neq 1$. First, we consider a perturbative treatment around $λ\approx 1$ and find that energies $E_n\propto n^{3/2}$ still holds as $n\to\infty$. To gain further insight into the Landau level structure for a maximum anisotropy, we turn to a semi-classical treatment that reveals interesting star-shaped orbits in phase space that close at infinity. This property is a manifestation of weakly localized states. Despite being infinite in length, these orbits enclose a finite phase space volume and permit finding a simple semi-classical formula for the energy, which again has the form as above. Our findings suggest that both isotropic and anisotropic cubic Dirac semi-metals should leave similar experimental imprints.

cond-mat.mes-hall↗
arXiv2023

Pseudo Electric Field and Pumping Valley Current in Graphene Nano-bubbles

The extremely high pseudo-magnetic field emerging in strained graphene suggests that an oscillating nano-deformation will induce a very high current even without electric bias. In this paper, we demonstrate the sub-terahertz (THz) dynamics of a valley-current and the corresponding charge pumping with a periodically excited nano-bubble. We discuss the amplitude of the pseudo-electric field and investigate the dependence of the pumped valley current on the different parameters of the system. Finally, we report the signature of extra-harmonics generation in the valley current that might lead to potential modern devices development operating in the nonlinear regime

cond-mat.mes-hall↗
arXiv2022

Floquet Hofstadter butterfly in trilayer graphene with a twisted top layer

The magnetic field generated Hofstadter butterfly in single-twist trilayer graphene (TLG) is investigated using circularly polarized light (CPL) and longitudinal light emanating from a waveguide. We show that single-twist TLG has two distinct chiral limits in the equilibrium state, and the central branch of the butterfly splits into two precisely degenerate components. The Hofstadter butterfly appears to be more discernible. We also discovered that CPL causes a large gap opening at the central branch of the Hofstadter butterfly energy spectrum and between the Landau levels, with a clear asymmetry corresponding to energy $E = 0$. We point out that for right-handed CPL, the central band shifts downward, in stark contrast to left-handed CPL, where the central band shifts upward. Finally, we investigated the effect of longitudinally polarized light, which originates from a waveguide. Interestingly, we observed that the chiral symmetries of the Hofstadter butterfly energy spectrum are broken for small driving strengths and get restored at large ones, contrary to what was observed in twisted bilayer graphene.

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↗