arXiv subjects

J. Milton Pereira Jr.

Publications and source records attributed to J. Milton Pereira Jr..

13 recordsLinked to original sources

arXiv2025

Electronic properties of multilayered Lieb, transition, and Kagome lattices

Based on the interconvertibility feature shared between monolayer Lieb and Kagome lattices, which allows mapping transition lattice's stages between these two limits ($π/2 \leqθ\leq 2π/3$), in this work we extend the recently proposed one-control ($θ$) parameter tight-binding model for the case of a multilayer Lieb-Kagome system, by considering the two most-common stacks: AA and AB (Bernal). We systematically study the band transformations between the two lattices by adjusting the interlayer hopping and distance, with or without considering the influence of the nearest interlayer neighbors, for different numbers of stacked layers, and under the application of an external perpendicular electric field. The energetic changes are understood from the perspective of the layer dependence of the pseudospin components and the total probability density distributions. The present framework provides an appropriate and straightforward theoretical approach to continuously investigate the evolution of electronic properties in the multilayer Lieb-Kagome system under various external effects.

cond-mat.mes-hall↗

arXiv2025

Topological phase transitions in strained Lieb-Kagome lattices

Lieb and Kagome lattices exhibit two-dimensional topological insulator behavior with $\mathbb{Z}_2$ topological classification when considering spin-orbit coupling. In this study, we used a general tight-binding Hamiltonian with a morphological control parameter $θ$ to describe the Lieb ($θ=π/2$), Kagome ($θ=2π/3$), and transition lattices ($π/2<θ<2π/3$) while considering intrinsic spin-orbit (ISO) coupling. We systematically investigated the effects of shear and uniaxial strains, applied along different crystallographic directions, on the electronic spectrum of these structures. Our findings reveal that these deformations can induce topological phase transitions by modifying the structural lattice angle associated with the interconversibility process between Lieb and Kagome, the amplitude of the strain, and the magnitude of the ISO coupling. These transitions are confirmed by the evolution of Berry curvature and by changes in the Chern number when the gap closes. Additionally, by analyzing hypothetical strain scenarios in which the hopping and ISO coupling parameters remain intentionally unchanged, our results demonstrated that the strain-induced phase transitions arise from changes in the hopping and ISO coupling parameters.

cond-mat.mes-hall↗

arXiv2018

Plasmons in bias-induced topological phase transition in black phosphorus

We investigate the plasmons in bilayer black phosphorus (BP) with bias-driven formation of Dirac cones, by developing an effective two-band Hamiltonian that captures this electronic transition with great accuracy. We show that the appearance of the Dirac cones lead to additional linearly dispersing acoustic plasmon mode, in conjunction to the conventional plasmon. In addition, the change in the Fermi surface topology from a disc to ring or dual pockets also modifies the dielectric loss.

cond-mat.mtrl-sci↗

arXiv2017

Multilayers black phosphorus: from tight-binding to continuum description

We investigate the electronic properties of $N$-layer black phosphorus by means of an analytical method based on a recently proposed tight-binding Hamiltonian involving $14$ hopping parameters. The method provides simple and accurate general expressions for the Hamiltonian of $N$-layer phosphorene, which are suitable for the study of electronic transport and optical properties of such systems, and the results show the features that emerge as the number of layers increases. In addition, we show that the $N$-layer problem can be translated into $N$ effective monolayer problems in the long wavelength approximation and, within this analytical picture, we obtain expressions for the energy gap and the effective masses for electrons and holes along the $N$-layer black phosphorus plane directions as function of the number of layers, as well as for the Landau levels as function of perpendicular magnetic field.

cond-mat.mes-hall↗

arXiv2010

Simplified model for the energy levels of quantum rings in single layer and bilayer graphene

Within a minimal model, we present analytical expressions for the eigenstates and eigenvalues of carriers confined in quantum rings in monolayer and bilayer graphene. The calculations were performed in the context of the continuum model, by solving the Dirac equation for a zero width ring geometry, i.e. by freezing out the carrier radial motion. We include the effect of an external magnetic field and show the appearance of Aharonov-Bohm oscillations and of a non-zero gap in the spectrum. Our minimal model gives insight in the energy spectrum of graphene-based quantum rings and models different aspects of finite width rings.

cond-mat.mes-hall↗

arXiv2007

Landau levels and oscillator strength in a biased bilayer of graphene

We obtain analytical expressions for the eigenstates and the Landau level spectrum of biased graphene bilayers in a magnetic field. The calculations are performed in the context of a four-band continuum model and generalize previous approximate results. Solutions are presented for the spectrum as a function of interlayer coupling, the potential difference between the layers and the magnetic field. The explicit expressions allow us to calculate the oscillator strength and the selection rules for electric dipole transitions between the Landau states. Some transitions are significantly shifted in energy relative to those in an unbiased bialyer and exhibit a very different magnetic field dependence.

cond-mat.mes-hall↗

arXiv2007

Tunable quantum dots in bilayer graphene

We demonstrate theoretically that quantum dots in bilayers of graphene can be realized. A position-dependent doping breaks the equivalence between the upper and lower layer and lifts the degeneracy of the positive and negative momentum states of the dot. Numerical results show the simultaneous presence of electron and hole confined states for certain doping profiles and a remarkable angular momentum dependence of the quantum dot spectrum which is in sharp contrast with that for conventional semiconductor quantum dots. We predict that the optical spectrum will consist of a series of non-equidistant peaks.

cond-mat.mes-hall↗

arXiv2007

Graphene-based resonant-tunneling strucures

Resonant electronic transmission through graphene-based double barriers (wells) is studied as a function of the incident wave vector, the widths and heights (depths) of the barriers (wells), and the separation between them. Resonant features in the transmission result from resonant electron states in the wells or hole states in the barriers and strongly influence the ballistic conductance of the structures.

cond-mat.mes-hall↗

arXiv2006

Magnetic interface states in graphene-based quantum wires

The electronic states of a finite-width graphene sheet in the presence of an electrostatic confining potential and a perpendicular magnetic field are investigated. The confining potential shifts the Landau levels inside the well and creates current-carrying states at or close to the interface with the barriers in addition to the edge states caused by the finite width of the sheet. Detailed energy spectra are given as a function of the quantum wire parameters. The dependence of the density of states on the confinement potential is evaluated for finite and zero magnetic field.

cond-mat.mes-hall↗

arXiv2006

Confined states and direction-dependent transmission in graphene quantum wells

We report the existence of confined massless fermion states in a graphene quantum well (QW) by means of analytical and numerical calculations. These states show an unusual quasi-linear dependence on the momentum parallel to the QW: their number depends on the wavevector and is constrained by electron-hole conversion in the barrier regions. An essential difference with non-relativistic electron states is a mixing between free and confined states at the edges of the free-particle continua, demonstrated by the direction-dependent resonant transmission across a potential well.

cond-mat.mtrl-sci↗

arXiv2004

Localised magnetic excitations of coupled impurities in a transverse Ising ferromagnet

A Green's function formalism is used to calculate the spectrum of excitations of two neighboring impurities implanted in a semi-infinite ferromagnetic. The equations of motion for the Green's functions are determined in the framework of the Ising model in a transverse field and results are given for the effect of the exchange coupling, position and orientation of the impurities on the spectra of localized spin wave modes.

cond-mat.mtrl-sci↗

arXiv2004

Green's function theory for a magnetic impurity layer in a ferromagnetic Ising film with transverse field

A Green's function formalism is used to calculate the spectrum of localized modes of an impurity layer implanted within a ferromagnetic thin film. The equations of motion for the Green's functions are determined in the framework of the Ising model in a transverse field. We show that depending on the thickness, exchange and effective field parameters, there is a ``crossover'' effect between the surface modes and impurity localized modes. For thicker films the results show that the degeneracy of the surface modes can be lifted by the presence of an impurity layer.

cond-mat.dis-nn↗

arXiv2003

Surface Plasmons on a Quasiperiodic Grating

A method is presented for calculating the frequencies of non-retarded surface plasmons propagating on a semi-inifinite medium with a surface profile described by a one-dimension quasiperiodic function. The profiles are generated, in analogy with previous work on quasiperiodic superlattices, by repeating unitary cells constructed according to an inflation rule. Dispersion relations are obtained for a semi-infinite free-electron metal as the active medium, with surface profiles obeying the Fibonacci and Thue-Morse sequences.

cond-mat↗