arXiv subjects

Igor S. S. de Oliveira

Publications and source records attributed to Igor S. S. de Oliveira.

7 recordsLinked to original sources

arXiv2026

A Unified Description of Dirac-Cone Anisotropies in Two Dimensions

Anisotropies in two-dimensional materials are responsible for a variety of effects that significantly modify their physical properties. In this paper, we present a covariant modification of the Dirac equation that incorporates anisotropies into the effective low-energy description around the Dirac point. The model is constructed by analogy with a Lorentz-violating extension of the Standard Model of elementary particles and yields a (2+1)-dimensional framework describing physical effects such as shifted, tilted, and distorted Dirac cones through its free parameters. The proposed model thus provides a general and unified framework in which distinct anisotropy-induced modifications of the Dirac spectrum and their combinations can be systematically characterized. We further apply the model to strained graphene and show that its effective parameters can be quantitatively extracted from first-principles electronic band structures while retaining a direct geometrical interpretation. These results establish a connection between the microscopic electronic structure and a material-independent effective description of anisotropic two-dimensional Dirac systems.

cond-mat.mes-hall↗

arXiv2026

Beyond Hexagonal Boron Nitride: First-Principles Study of Pentaoctite-BN and Pop-BN Monolayers

We investigate two novel non-hexagonal boron nitride monolayers, pentaoctite-BN (PO-BN) and pop-BN (PP-BN), using first-principles calculations. Their structural, electronic, mechanical, vibrational, thermal, and optical properties are systematically analyzed to assess their stability and potential applications. Despite being metastable with respect to hexagonal BN, both polymorphs satisfy the criteria for dynamical, mechanical, and thermal stability, indicating that they are viable two-dimensional materials. Both systems are indirect-gap semiconductors whose electronic states near the band edges are dominated by out-of-plane pz orbitals. Their distinct pentagon-octagon ring networks also give rise to different in-plane elastic anisotropies. Many-body optical calculations reveal strong excitonic effects and pronounced polarization-dependent optical absorption, with lattice engineering shifting the optical response from the ultraviolet toward the visible and infrared regions. These findings demonstrate that engineering non-hexagonal lattice architectures provides an effective strategy for tuning the electronic and optical properties of two-dimensional BN, highlighting PO-BN and PP-BN as promising candidates for future optoelectronic and photonic applications.

cond-mat.mtrl-sci↗

arXiv2026

Descriptor-Based Classification of Interfacial Electronic Coupling in Janus XP3-Based 2D Heterostructures

Understanding and controlling interfacial electronic coupling in two-dimensional (2D) heterostructures is essential for designing functional materials for electronic, optoelectronic, and catalytic applications. Here, we investigate vertical heterobilayers constructed from two distinct XP3 monolayers (X = As, Ge, Sb, Bi, Sn, Al, Ga, and Pb) using first-principles density functional theory. The resulting Janus heterobilayers are energetically favorable and elastically stable, with electronic band gaps ranging from metallic and near-metallic to semiconducting regimes. Interlayer interactions induce significant band renormalization, including transitions between type I and type II alignment upon structural relaxation. To rationalize these effects, we establish a descriptor-based framework based on the metal metal interlayer distance, interfacial electron localization, and Bader charge redistribution. This combined analysis discriminates vdW-like, polar covalent, and ionic interaction regimes, with systematic trends governed by the average atomic number of the constituent elements. Optical absorption calculations indicate visible-to-near-infrared activity in selected systems, and band-edge alignment identifies promising candidates for selective redox processes. Overall, the proposed descriptor-based strategy provides a physically grounded route for identifying and engineering interfacial coupling in XP3 heterostructures and can be extended to other classes of two-dimensional material interfaces.

cond-mat.mtrl-sci↗

arXiv2025

First-principles study of metal-biphenylene interfaces: structural, electronic, and catalytic properties

We employ first-principles density functional theory (DFT) calculations to investigate the structural, electronic, and catalytic properties of biphenylene supported on various metal substrates. The substrates considered are the (111) surfaces of Ag, Au, Ni, Pd, Pt, Cu, Al, and the Cu$_3$Au alloy. Our results reveal how the interaction between biphenylene and the substrate governs its stability, degree of corrugation, electronic hybridization, and interfacial charge transfer. In particular, we observe a clear trend where weakly interacting metals preserve the intrinsic features of biphenylene, while more reactive substrates lead to significant structural and electronic modifications. We further evaluate the hydrogen evolution reaction (HER) activity of these systems, showing that certain metal supports, especially Pd, Pt, Ag, and Cu, can enhance the catalytic performance of biphenylene. Notably, Ag and Cu combine good catalytic activity with lower cost and chemical stability, offering a promising balance for practical applications. These findings provide insights into the design of biphenylene-metal interfaces, supporting their use in next-generation electronic and catalytic devices.

cond-mat.mtrl-sci↗

arXiv2025

Catenary-like rippled biphenylene/graphene lateral heterojunction

In this study, we conduct a first-principles analysis to explore the structural and electronic properties of curved biphenylene/graphene lateral junctions (BPN/G). We start our investigation focusing on the energetic stability of BPN/G by varying the width of the graphene region, BPN/Gn. The electronic structure of BPN/Gn reveals (i) the formation of metallic channels mostly localized along the BPN stripes, where (ii) the features of the energy bands near the Fermi level are ruled by the width (n) of the graphene regions, Gn. In the sequence, we find that the hydrogenation of BPN/Gn results in a semiconductor system with a catenary-like rippled geometry. The electronic states of the hydrogenated system are mainly confined in the curved Gn regions, and the dependence of the bandgap on the width of Gn is similar to that of hydrogenated armchair graphene nanoribbons. The effects of curvature on the electronic structure, analyzed in terms of external mechanical strain, revealed that the increase/decrease of the band gap is also dictated by the width of the Gn region. Further electronic transport calculations reveal a combination of strong transmission anisotropy and the emergence of negative differential resistance. Based on these findings, we believe that rippled biphenylene/graphene systems can be useful for the design of two-dimensional nanodevices.

cond-mat.mtrl-sci↗

arXiv2024

Group-IV Pentaoctite: A New 2D Material Family

This study investigates the structural, mechanical, and electronic properties of novel two-dimensional (2D) pentaoctite (PO) monolayers composed of group-IV elements (PO-C, PO-Si, PO-Ge, and PO-Sn) using first-principles calculations. Stability is explored through phonon spectra and ab initio molecular dynamics simulations, confirming that all proposed structures are dynamically and thermally stable. Mechanical analysis shows that PO-C monolayers exhibit exceptional rigidity, while the others demonstrate greater flexibility, making them suitable for applications in foldable materials. The electronic properties show semimetallic behavior for PO-C and metallic behavior for PO-Si, while PO-Ge and PO-Sn possess narrow band gaps, positioning them as promising candidates for semiconductor applications. Additionally, PO-C exhibits potential as an efficient catalyst for the hydrogen evolution reaction (HER), with strain engineering further enhancing its catalytic performance. These findings suggest a wide range of technological applications, from nanoelectronics and nanomechanics to metal-free catalysis in sustainable energy production.

cond-mat.mes-hall↗

arXiv2023

Unveiling the electronic properties of BiP$_3$ triphosphide from bulk to graphene-based heterostructure by first-principles calculations

Triphosphides, with a chemical formula of XP$_3$ (X is a group IIIA, IVA, or VA element), have recently attracted much attention due to their great potential in several applications. Here, using density functional theory calculations, we describe for the first time the structural and electronic properties of the bulk bismuth triphosphide (BiP$_3$). Phonon spectra and molecular dynamics simulations confirm that the 3D crystal of BiP$_3$ is a metal thermodynamically stable with no bandgap. Unlike the bulk, the mono-, bi-, tri-, and tetra-layers of BiP$_3$ are semiconductors with a bandgap ranging from 1.4 to 0.06 eV. However, stackings with more than five layers exhibit metallic behavior equal to the bulk. The results show that quantum confinement is a powerful tool for tuning the electronic properties of BiP$_3$ triphosphide, making it suitable for technological applications. Building on this, the electronic properties of van der Waals heterostructure constructed by graphene (G) and the BiP$_3$ monolayer (m-BiP$_3$) were investigated. Our results show that the Dirac cone in graphene remains intact in this heterostructure. At the equilibrium interlayer distance, the G/m-BiP$_3$ forms an n-type contact with a Schottky barrier height of 0.5 eV. It is worth noting that the SHB in the G/m-BiP$_3$ heterostructure can be adjusted by changing the interlayer distance or applying a transverse electric field. Thus, we show that few-layers BiP$_3$ is an interesting material for realizing nanoelectronic and optoelectronic devices and is an excellent option for designing Schottky nanoelectronic devices.

cond-mat.mtrl-sci↗