arXiv subjects

Jhao-Ying Wu

Publications and source records attributed to Jhao-Ying Wu.

At least 19 recordsLinked to original sources

arXiv2025

Stacking-Dependent Electronic Properties in GaSe/GaTe Heterobilayers: A First-Principles Study

In this study, we use first-principles calculations to investigate the stacking-dependent electronic properties of GaSe/GaTe van der Waals heterobilayers. By analyzing five representative stacking configurations--AA, AA$'$, A$'$C, A$'$B, and AB--we show that interlayer atomic registry affects orbital hybridization and interfacial interactions, leading to distinct electronic structures and stabilities. Projected density of states analyses reveal valence and conduction band edges arise from orbitals localized in different layers, confirming a type-II band alignment that facilitates spatial charge separation. Orbital contributions and spectral features vary with stacking, reflecting how interlayer coupling modulates hybridization and electronic behavior. This study provides atomic-level insights for designing and optimizing layered heterostructures in nanoelectronic devices.

cond-mat.mtrl-sci↗

arXiv2019

Anomalous magneto-transport properties of bilayer phosphorene

The magneto-transport properties of phosphorene are investigated by employing the generalized tight-binding model to calculate the energy bands. For bilayer phosphorene, a composite magnetic and electric field is shown to induce a feature-rich Landau level (LL) spectrum which includes two subgroups of low-lying LLs. The two subgroups possess distinct features in level spacings, quantum numbers, as well as field dependencies. These together lead to anomalous quantum Hall (QH) conductivities which include a well-shape, staircase and composite quantum structures with steps having varying heights and widths. The Fermi energy-magnetic field-Hall conductivity ($E_{F}-B_{z}-σ_{xy}$) and Fermi energy-electric field-Hall conductivity ($E_{F}-E_{z}-σ_{xy}$) phase diagrams clearly exhibit oscillatory behaviors and cross-over from integer to half-integer QH effect. The predicted results should be verifiable by magneto-transport measurements in a dual-gated system.

cond-mat.mes-hall↗

arXiv2019

Diverse quantization phenomena in layered materials

The diverse quantization phenomena in 2D condensed-matter systems, being due to a uniform perpendicular magnetic field and the geometry-created lattice symmetries, are the focuses of this book. They cover the diversified magneto-electronic properties, the various magneto-optical selection rules, the unusual quantum Hall conductivities, and the single- and many-particle magneto-Coulomb excitations. The rich and unique behaviors are clearly revealed in few-layer graphene systems with the distinct stacking configurations, the stacking-modulated structures, and the silicon-doped lattices, bilayer silicene/germanene systems with the bottom-top and bottom-bottom buckling structures, monolayer and bilayer phosphorene systems, and quantum topological insulators. The generalized tight-binding model, the static and dynamic Kubo formulas, and the random-phase approximation, are developed/modified to thoroughly explore the fundamental properties and propose the concise physical pictures. The different high-resolution experimental measurements are discussed in detail, and they are consistent with the theoretical predictions.

physics.comp-ph↗

arXiv2019

Coulomb excitations and decays in graphene-related systems

The layered graphene systems exhibit the rich and unique excitation spectra arising from the electron-electron Coulomb interactions. The generalized tight-binding model is developed to cover the planar/buckled/cylindrical structures, specific lattice symmetries, different layer numbers, distinct configurations, one-three dimensions, complicated intralayer and interlayer hopping integrals, electric field, magnetic quantization; any temperatures and dopings simultaneously. Furthermore, we modify the random-phase approximation to agree with the layer-dependent Coulomb potentials with the Dyson equation, so that these two methods can match with other under various external fields. The electron-hole excitations and plasmon modes are greatly diversified by the above-mentioned critical factors; that is, there exist the diverse (momentum. frequency)-related phase diagrams. They provide very effective deexcitation scatterings and thus dominate the Coulomb decay rates. Graphene, silicene and germanene might quite differ from one another in Coulomb excitations and decays because of the strength of spin-orbital coupling. Part of theoretical predictions have confirmed the experimental measurements, and most of them require the further examinations. Comparisons with the other models are also made in detail.

physics.comp-ph↗

arXiv2018

Unusual Electronic excitations in ABA trilayer graphene

The tight-binding model is closely associated with the modified random-phase approximation to thoroughly explore the electron-electron interactions in trilayer AB-stacked graphene. The intralayer and interlayer atomic/Coulomb interactions dominate the collective and electron-hole excitations. The unusual energy bands are directly reflected in the diverse transferred momentum-frequency phase diagrams. There exist three kinds of plasmon modes during the variation of the doping level, being accompanied with the complicated intraband and interband single-particle excitations. The excitation behaviors are greatly diversified by the number of layers. The theoretical predictions require the high-resolution experimental examinations.

cond-mat.mes-hall↗

arXiv2018

The diverse magneto-optical selection rules in bilayer black phosphorus

The magneto-optical properties of bilayer phosphorene is investigated by the generalized tight-binding model and the gradient approximation. The vertical inter-Landau-level transitions, being sensitive to the polarization directions, are mainly determined by the spatial symmetries of sub-envelope functions on the distinct sublattices. The anisotropic excitations strongly depend on the electric and magnetic fields. A perpendicular uniform electric field could greatly diversify the selection rule, frequency, intensity, number and form of symmetric absorption peaks. Specifically, the unusual magneto-optical properties appear beyond the critical field as a result of two subgroups of Landau levels with the main and side modes. The rich and unique magneto-absorption spectra arise from the very close relations among the geometric structures, multiple intralayer and interlayer hopping integrals, and composite external fields.

cond-mat.mes-hall↗

arXiv2017

Coulomb scattering rates of excited states in germanene

The excited conduction electrons, conduction holes and valence holes in monolayer germanene exhibit the feature-rich Coulomb decay rates. The dexcitation processes are studied using the Matsubara's screened exchange energy. They might utilize the intraband single-particle excitations (SPEs), the interband SPEs, and three kinds of plasmon modes, depending on the quasiparticle states and the Fermi energies. The low-lying valence holes can decay by the undamped acoustic plasmon, so that they present very fast Coulomb deexcitations, the non-monotonous energy dependence and the anisotropic behavior. However, the low-energy conduction holes and electrons behave as 2D electron gas. The high-energy conduction states and the deep-energy valence ones are similar in the available deexcitation channels and the dependence of decay rate on wave vector k.

cond-mat.mtrl-sci↗

arXiv2017

Novel Magnetic Quantization of Bismuthene

The generalized tight-binding model, being based on the spin-dependent sublattices, is developed to explore the magnetic quantization of monolayer bismuthene. The sp$^{3}$ orbital hybridizations, site energies, nearest and next-nearest hopping integrals, spin-orbital interactions and magnetic field (${B_{z}}$ ${\hat{z}}$) are taken into account simultaneously. There exist three groups of low-lying Landau levels (LLs), in which they are mainly from the (6p$_{x}$,6p$_{y}$,6p$_{z}$) orbitals, and only the first group belongs to the unoccupied conduction states. Furthermore, each group is further split into the spin-up- and spin-down-dominated subgroups. The six subgroups present the rich and unique $B_{z}$-dependent LL energy spectra, covering the specific or arc-shaped $% B_{z}$-dependences, the normal/irregular spin-split energies, and the non-crossing/crossing/anti-crossing behaviors. Specially, the second group of valence LLs near the Fermi level can create the frequent inter-subgroup LL anti-crossings since the main and side modes are comparable. The main features of energy spectra can create the special structures in density of states.

cond-mat.mtrl-sci↗

arXiv2016

Field-created diverse quantizations in phosphorenes

Electronic properties of few-layer phosphorenes are investigated by the generalized tight-binding model. They are greatly diversified by the electric and magnetic fields ($E_z$ and $B_z$). The $E_z$-induced gap transition, Dirac cones, oscillatory bands and critical points are present in bilayer system, but absent in monolayer one. The diverse magnetic quantization phenomena cover the coexistent two subgroups of Landau levels, the uniform and non-uniform energy spacings, and the crossing and anti-crossing behaviors. Specifically, the wavefunctions exhibit the dramatic changes between the well-behaved and multi-mode oscillations. The feature-rich energy spectra are reveled in density of states as .many special structures which could be verified from scanning tunneling spectroscopy.

cond-mat.mtrl-sci↗

arXiv2016

Coulomb excitations of monolayer germanene

The feature-rich electronic excitations of monolayer germanene lie in the significant spin-orbital coupling and the buckled structure. The collective and single- particle excitations are diversified by the magnitude and direction of transferred momentum, the Fermi energy and the gate voltage. There are four kinds of plasmon modes, according to the unique frequency- and momentum-dependent phase diagrams. They behave as two-dimensional acoustic modes at long wavelength. However, for the larger momenta, they might change into another kind of undamped plasmons, become the seriously suppressed modes in the heavy intraband e-h excitations, keep the same undamped plasmons, or decline and then vanish in the strong interband e-h excitations. Germanene, silicene and graphene are quite different from one another in the main features of the diverse plasmon modes.

physics.comp-ph↗

arXiv2015

Novel Magnetic Quantization of sp$^{3}$ Bonding in Monolayer Tinene

A generalized tight-binding model, which is based on the subenvelope functions of the different sublattices, is developed to explore the novel magnetic quantization in monolayer gray tin. The effects due to the $sp^{3}$ bonding, the spin-orbital coupling, the magnetic field and the electric field are simultaneously taken into consideration. The unique magneto-electronic properties lie in two groups of low-lying Landau levels, with different orbital components, localization centers, state degeneracy, spin configurations, and magnetic- and electric-field dependences. The first and second groups mainly come from the $5p_{z}$ and ($5p_{x}$,$5p_{y}$) orbitals, respectively. Their Landau-level splittings are, respectively, induced by the electric field and spin-orbital interactions. The intragroup anti-crossings are only revealed in the former. The unique tinene Landau levels are absent in graphene, silicene and germanene.

cond-mat.mes-hall↗

arXiv2015

Feature-rich electronic excitations in external fields of 2D silicene

Electronic Coulomb excitations in monolayer silicene are investigated by using the Lindhard dielectric function and a newly developed generalized tight-binding model (G-TBM). G-TBM simultaneously contains the atomic interactions, the spin-orbit coupling, the Coulomb interactions, and the various external fields at an arbitrary chemical potential. We exhibit the calculation results of the electrically tunable magnetoplasmons and the strong magnetic field modulation of plasmon behaviors. The two intriguing phenomena are well explained by determining the dominant transition channels in the dielectric function and through understanding the electron behavior under the multiple interactions (intrinsic and external). A further tunability of the plasmon features is demonstrated with the momentum transfer and the Fermi energy. The methodological strategy could be extended to several other 2D materials like germanene and stanene, and might open a pathway to search a better system in nanoplasmonic applications.

cond-mat.mes-hall↗

arXiv2015

Environmental Effects on the Terahertz Surface Plasmons in Epitaxial Graphene

In this paper, we predict the existence of low-frequency nonlocal plasmon excitations at the vacuum-surface interface of a superlattice of $N$ graphene layers interacting with a thick conducting substrate. This is different from graphite which allows inter-layer hopping. A dispersion function is derived which incorporates the polarization function of the graphene monolayers (MLGs) and the dispersion function of a semi-infinite electron liquid at whose surface the electrons scatter specularly. We find that this surface plasmon-polariton is not damped by the particle-hole excitations (PHE's) or the bulk modes and separates below the continuum mini-band of bulk plasmon modes. For a conducting substrate with surface plasmon frequency $ω_s=ω_p/\sqrt{2}$, the surface plasmon frequency of the hybrid structure always lies below $ω_s$. The intensity of this mode depends on the distance of the graphene layers from the surface of the conductor, the energy band gap between the valence and conduction bands of MLG and, most importantly, on the number of two-dimensional (2D) layers. Furthermore, the hybrid structure has no surface plasmon for a sufficiently large number ($N\stackrel{>}{\sim} 7$) of layers. The existence of two plasmons with different dispersion relations indicates that quasiparticles with different group velocity may coexist for various ranges of wavelength which is determined by the number of layers in the superlattice.

cond-mat.mes-hall↗

arXiv2015

Magnetic quantization in multilayer graphenes

Essential properties of multilayer graphenes are diversified by the number of layers and the stacking configurations. For an $N$-layer system, Landau levels are divided into $N$ groups, with each identified by a dominant sublattice associated with the stacking configuration. We focus on the main characteristics of Landau levels, including the degeneracy, wave functions, quantum numbers, onset energies, field-dependent energy spectra, semiconductor-metal transitions, and crossing patterns, which are reflected in the magneto-optical spectroscopy, scanning tunneling spectroscopy, and quantum transport experiments. The Landau levels in AA-stacked graphene are responsible for multiple Dirac cones, while in AB-stacked graphene the Dirac properties depend on the number of graphene layers, and in ABC-stacked graphene the low-lying levels are related to surface states. The Landau-level mixing leads to anticrossings patterns in energy spectra, which are seen for intergroup Landau levels in AB-stacked graphene, while in particular, a formation of both intergroup and intragroup anticrossings is observed in ABC-stacked graphene. The aforementioned magneto-electronic properties lead to diverse optical spectra, plasma spectra, and transport properties when the stacking order and the number of layers are varied. The calculations are in agreement with optical and transport experiments, and novel features that have not yet been verified experimentally are presented.

physics.comp-ph↗

arXiv2015

The effect of perpendicular electric field on Temperature-induced plasmon excitations for intrinsic silicene

We use the tight-binding model and the random-phase approximation to investigate the intrinsic plasmon in silicene. At finite temperatures, an undamped plasmon is generated from the interplay between the intraband and the interband-gap transitions. The extent of the plasmon existence range in terms of momentum and temperature, which is dependent on the size of single-particle-excitation gap, is further tuned by applying a perpendicular electric field. The plasmon becomes damped in the interband-excitation region. A low damped zone is created by the field-induced spin split. The field-dependent plasmon spectrum shows a strong tunability in plasmon intensity and spectral bandwidth. This could make silicene a very suitable candidate for plasmonic applications.

cond-mat.mtrl-sci↗

arXiv2014

Magneto-optical selection rules of curved graphene nanoribbons and carbon nanotubes

We derive the generalized magneto-absorption spectra for curved graphene nanorib- bons and carbon nanotubes by using the Peierls tight-binding model. The main spectral characteristics and the optical selection rules result from the cooperative or competitive relationships between the geometric structure and a magnetic field. In curved ribbons, the dominant selection rule remains unchanged during the variation of the curvature. When the arc angle increases, the prominent peaks are split, with some even vanishing as the angle exceeds a critical value. In carbon nanotubes, the angular-momentum coupling induces extra selection rules, of which more are revealed due to the increase of either (both) of the factors: tube diameter and field strength. Particularly once the two factors exceed certain critical values, the optical spectra could reflect the quasi-Landau-level structures. The identifying features of the spec- tra provide insight into optical excitations for curved systems with either open or closed boundary condition.

cond-mat.mtrl-sci↗

arXiv2014

Electrically tunable plasma excitations in AA-stacking multilayer graphene

We use a tight-binding model and the random-phase approximation to study the Coulomb excitations in simple-hexagonal-stacking multilayer graphene and discuss the field effects. The calculation results include the energy bands, the response functions, and the plasmon dispersions. A perpendicular electric field is predicted to induce significant charge transfer and thus capable of manipulating the energy, intensity, and the number of plasmon modes. This could be further validated by inelastic light scattering or electron-energy-loss spectroscopy.

cond-mat.mtrl-sci↗

arXiv2014

Combined Effect of Stacking and Magnetic Field on Plasmon Excitations in Bilayer Graphene

The electronic excitations of bilayer graphene (BLG) under a magnetic field are investigated with the use of the Peierls tight-binding model in conjunction with random-phase approximation (RPA). The interlayer atomic interactions, interlayer Coulomb interactions, and magnetic field effects are simultaneously included in the dielectric-function matrix. That enables us to derive the magneto-Coulomb-excitation spectrum of different stacking structures. The two typical arrangements of BLGs, AB and AA, are considered in this article. AB-BLG exhibits many discrete energy-loss peaks, which correspond to the quantization of electron energies. On the other hand, the AA-BLG spectra possess a unique and pronounced peak at low frequency. This peak represents the collective excitation of the entire low-frequency Landau states. The dependence of the energy-loss peaks on the momentum transfer and the magnetic field strength is presented. Accordingly, two kinds of plasmon modes produced by the layer stacking are clearly distinguished.

cond-mat.mes-hall↗