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We introduce a refined tight-binding (TB) model for Pt-based jacutingaite materials Pt$_{2}N$X$_{3}$, ($N$ = Zn, Cd, Hg; X = S, Se, Te), offering a detailed representation of the low-energy physics of its monolayers. This model incorporates all elements with significant spin-orbit coupling contributions, which are essential for understanding the topological energy gaps in these materials. Through comparison with first-principles calculations, we meticulously fitted the TB parameters, ensuring an accurate depiction of the energy bands near the Fermi level. Our model reveals the intricate interplay between the Pt $3e$ and $N$ metal orbitals, forming distinct kagome and honeycomb lattice structures. Applying this model, we explore the edge states of Pt-based jacutingaite monolayer nanoribbons, highlighting the sensitivity of the topological edge states dispersion bands to the nanostructures geometric configurations. These insights not only deepen our understanding of jacutingaite materials but also assist in tailoring their electronic properties for future applications., Comment: Accepted for publication in the Journal of Physics: Condensed Matter on October 4, 2024

The recent synthesis of Goldene, a 2D atomic monolayer of gold, has opened new avenues in exploring novel materials. However, the question of when multilayer Goldene transitions into bulk gold remains unresolved. This study used density functional theory calculations to address this fundamental question. Our findings reveal that multilayer Goldene retains an AA-like stacking configuration of up to six layers, with no observation of Bernal-like stacking as seen in graphene. Goldene spontaneously transitions to a bulk-like gold structure at seven layers, adopting a rhombohedral (ABC-like) stacking characteristic of bulk face-centered cubic (FCC) gold. The atomic arrangement converges entirely to the bulk gold lattice for more than ten layers. Quantum confinement significantly impacts the electronic properties, with monolayer and bulk Goldene exhibiting a single Dirac cone at the X-point of the Brillouin zone. In contrast, multilayer Goldene shows two Dirac cones at the X- and Y-points. Additionally, monolayer Goldene exhibits anisotropic optical absorption, which is absent in bulk gold. This study provides a deeper understanding of multilayer Goldene's structural and electronic properties and stacked 2D materials in general., Comment: 12 pages

The thermal conductivity of two-dimensional (2D) materials is critical in determining their suitability for several applications, from electronics to thermal management. In this study, we have used Molecular Dynamics (MD) simulations to investigate the thermal conductivity and phononic properties of 8-16-4(Sun)-Graphyne, a recently proposed 2D carbon allotrope. The thermal conductivity was estimated using reverse non-equilibrium MD simulations following the Muuller-Plathe approach, revealing a strong dependence on system size. Phonon dispersion calculations confirm the stability of Sun-GY while also showing a significant decrease in thermal conductivity compared to graphene. This decrease is attributed to acetylenic bonds, which enhance phonon scattering. Spectral analysis further revealed that Sun-GY exhibits lower phonon group velocities and increased phonon scattering, mainly due to interactions between acoustic and optical modes. Sun-GY presents an intrinsic thermal conductivity of approximately 24.6 W/mK, much lower than graphene, making it a promising candidate for applications that require materials with reduced thermal transport properties., Comment: 11 pages, 05 figures

We investigate the electronic properties of nanoribbons made out of monolayer Lieb, transition, and kagome lattices using the tight-binding model with a generic Hamiltonian. It allows us to map the evolutionary stages of the interconvertibility process between Lieb and kagome nanoribbons by means of only one control parameter. Results for the energy spectra, the density of states, and spatial probability density distributions are discussed for nanoribbons with three types of edges: straight, bearded, and asymmetric. We explore for different nanoribbon terminations: (i) the semiconductor-metallic transition due to the interconvertibility of the Lieb and kagome lattices, (ii) the effect of both nanoribbon width and inclusion of the next-nearest-neighbor hopping term on the degeneracy of the quasi-flat states, (iii) the behavior of the energy gap versus the nanoribbon width, (iv) the existence and evolution of edge states, and (v) the nodal spatial distributions of the total probability densities of the non-dispersive states., Comment: 21 pages, 12 figures

Recently, a new 2D carbon allotrope called Irida-Graphene (Irida-G) was proposed. Irida-G consists of a flat sheet topologically arranged into 3-6-8 carbon rings exhibiting metallic and non-magnetic properties. In this study, we investigated the thermal transport properties of Irida-G using classical reactive molecular dynamics simulations. The findings indicate that Irida-G has an intrinsic thermal conductivity of approximately 215 W/mK at room temperature, significantly lower than that of pristine graphene. This decrease is due to characteristic phonon scattering within Irida-G's porous structure. Additionally, the phonon group velocities and vibrational density of states for Irida-G were analyzed, revealing reduced average phonon group velocities compared to graphene. The thermal conductivity of Irida-G is isotropic and shows significant size effects, transitioning from ballistic to diffusive heat transport regimes as the system length increases. These results suggest that while Irida-G has lower thermal conductivity than graphene, it still holds potential for specific thermal management applications, sharing characteristics with other two-dimensional materials., Comment: 09 pages, 06 figures

Internet of Things (IoT) devices are increasingly pervasive and essential components in enabling new applications and services. However, their widespread use also exposes them to exploitable vulnerabilities and flaws that can lead to significant losses. In this context, ensuring robust cybersecurity measures is essential to protect IoT devices from malicious attacks. However, the current solutions that provide flexible policy specifications and higher security levels for IoT devices are scarce. To address this gap, we introduce T800, a low-resource packet filter that utilizes machine learning (ML) algorithms to classify packets in IoT devices. We present a detailed performance benchmarking framework and demonstrate T800's effectiveness on the ESP32 system-on-chip microcontroller and ESP-IDF framework. Our evaluation shows that T800 is an efficient solution that increases device computational capacity by excluding unsolicited malicious traffic from the processing pipeline. Additionally, T800 is adaptable to different systems and provides a well-documented performance evaluation strategy for security ML-based mechanisms on ESP32-based IoT systems. Our research contributes to improving the cybersecurity of resource-constrained IoT devices and provides a scalable, efficient solution that can be used to enhance the security of IoT systems., Comment: 11 pages, under review

With the increase of variable renewable energy sources (VRES) share in electricity systems, manystudies were developed in order to determine their optimal technological and spatial mix. Modern PortfolioTheory (MPT) has been frequently applied in this context. However, some crucial aspects, important inenergy planning, are not addressed by these analyses. We, therefore, propose several improvements andevaluate how each change in formulation impacts results. More specifically, we address generation costs, system demand, and firm energy output, present a formal model and apply it to the case of Brazil. Wefound that, after including our proposed modifications, the resulting efficient frontier differs strongly fromthe one obtained in the original formulation. Portfolios with high output standard deviation are not ableto provide a firm output level at competitive costs. Furthermore, we show that diversification plays animportant role in smoothing output from VRES portfolios, Comment: Comments welcome, 25 pages

Within the effective-mass approximation, we theoretically investigated the electronic and transport properties of 2D semiconductor quantum wires (QWs) with anisotropic effective masses and different orientations with respect to the anisotropic axis. The energy levels in the absence and presence of an external magnetic field are analytically calculated, showing: (i) a strong dependence on the spacing of energy levels related to the alignment QW angle and the anisotropy axis; and (ii) for non-null magnetic field, the quantum Hall edge states are significantly affected by the edge orientation. Moreover, by means of the split-operator technique, we analyzed the time evolution of wavepackets in straight and V-shaped anisotropic QWs and compared the transmission probabilities with those of isotropic systems. In the anisotropic case we found damped oscillations in the average values of velocity in both x and y directions for a symmetric Gaussian wavepacket propagating along a straight wide QW, with the oscillation being more evident as the non-collinearity between the group velocity and momentum vectors increases., Comment: 12 pages, 11 figures

In this work we describe a proposal for a graphene-based nanostructure that modulates electric current even in the absence of a gap in the band structure. The device consists of a graphene p-n junction that acts as a Veselago lens that focuses ballistic electrons on the output lead. Applying external (electric and magnetic) fields changes the position of the output focus, reducing the transmission. Such device can be applied to low power field effect transistors, which can benefit from graphene's high electronic mobility.

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., Comment: 5 pages, 3 figures

We study the addition energy spectra of phosphorene quantum dots focusing on the role of dot size, edges passivation, number of layers and dielectric constant of the substrate where the dots are deposited. We show that for sufficiently low dielectric constants ($\varepsilon_{sub} < 4$), Coulomb blockade can be observed in dot sizes larger than 10 nm, for both passivated and unpassivated edges. For higher dielectric constants (up to $\varepsilon_{sub} = 30$), Coulomb blockade demands smaller dot sizes, but this depends whether the edges are passivated or not. This dramatic role played by the substrate is expected to impact on the development of application based on phosphorene quantum dots.

We investigate the effects of a perpendicular electric field applied to multilayer phosphorene nanoribbons with zigzag and armchair edges. Within the context of the tight-binding model, we explore the electronic properties of these systems giving emphasis to the appearance of Dirac-like spectra, a transition that occurs when the gate density associated with the applied displacement field is greater than the critical value $n_c$. We show that the confinement properties and the screening effects in such systems play an important role on the determination of $n_c$, suggesting a scheme to determine the thickness, width and edge orientation of multilayered phosphorene nanoribbons. We also explore how this transition affects the electronic transport properties of such systems., Comment: 6 pages, 5 figures

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., Comment: 12 pages, 7 figures

Dielectric screening is greatly important to an accurate calculation of the exciton binding energies in two-dimensional materials. In this work, we calculate the dielectric function and 2D polarizability of multilayer (up to three) phosphorene sheets using Density Functional Theory. The 2D polarizabilities are then used in the dielectric screening of the excitonic interaction in multilayer phosphorene quantum dots. In the limit of large quantum dots, excitonic gaps are shown to exhibit very good agreement with state-of-the-art measurements of the optical gaps of multilayer phosphorene sheets deposited in different substrates.

We theoretically study a current switch that exploits the phase acquired by a charge carrier as it tunnels through a potential barrier in graphene. The system acts as an interferometer based on an armchair graphene quantum ring, where the phase difference between interfering electronic wave functions for each path can be controlled by tuning either the height or the width of a potential barrier in the ring arms. By varying the parameters of the potential barriers the interference can become completely destructive. We demonstrate how this interference effect can be used for developing a simple graphene-based logic gate with high on/off ratio, Comment: 6 pages, 6 figures