Band structures of graphene nanoscrolls and their dispersion relation near the Fermi point

RSC Advances ◽  
2016 ◽  
Vol 6 (45) ◽  
pp. 38753-38760 ◽  
Author(s):  
Mohsen Khaledian ◽  
Razali Ismail ◽  
Elnaz Akbari
Keyword(s):  
Dispersion Relation ◽  
Band Structure ◽  
Physical Structure ◽  
Band Structures ◽  
Different Types ◽  
Graphene Nanoscrolls ◽  
Fermi Point

We studied the physical structure and band structure of different types of graphene nanoscrolls.

Band Structure and Optical Gain of 1.3 um GaAsSbN/GaAs Compressively Strained Quantum Well Laser

2007 ◽  
Vol 31 ◽  
pp. 95-97
Author(s):  
B. Dong ◽  
W.J. Fan ◽  
Y.X. Dang
Keyword(s):  
Band Structure ◽  
Quantum Well ◽  
Optical Gain ◽  
Band Structures ◽  
Quantum Well Laser ◽  
Suitable Combination ◽  
Gain Spectra ◽  
Strained Quantum Well

The band structures and optical gain spectra of GaAsSbN/GaAs compressively strained quantum well (QW) were studied using 10-band k.p approach. We found that a higher Sb and N composition in the quantum well and a thicker well give longer emitting wavelength. The result also shows a suitable combination of Sb and N composition, and QW thickness can achieve 1.3 μm lasing. And, the optical gain spectra with different carrier concentrations will be obtained.

scholarly journals Accurate Prediction of Band Structure of FeS2: A Hard Quest of Advanced First-Principles Approaches

2021 ◽  
Vol 9 ◽  
Author(s):  
Min-Ye Zhang ◽  
Hong Jiang
Keyword(s):  
Band Structure ◽  
First Principles ◽  
High Energy ◽  
Accurate Prediction ◽  
Band Gaps ◽  
Full Potential ◽  
Band Structures ◽  
Electronic Band ◽  
Fundamental Band ◽  
Hybrid Functionals

The pyrite and marcasite polymorphs of FeS2 have attracted considerable interests for their potential applications in optoelectronic devices because of their appropriate electronic and optical properties. Controversies regarding their fundamental band gaps remain in both experimental and theoretical materials research of FeS2. In this work, we present a systematic theoretical investigation into the electronic band structures of the two polymorphs by using many-body perturbation theory with the GW approximation implemented in the full-potential linearized augmented plane waves (FP-LAPW) framework. By comparing the quasi-particle (QP) band structures computed with the conventional LAPW basis and the one extended by high-energy local orbitals (HLOs), denoted as LAPW + HLOs, we find that one-shot or partially self-consistent GW (G0W0 and GW0, respectively) on top of the Perdew-Burke-Ernzerhof (PBE) generalized gradient approximation with a converged LAPW + HLOs basis is able to remedy the artifact reported in the previous GW calculations, and leads to overall good agreement with experiment for the fundamental band gaps of the two polymorphs. Density of states calculated from G0W0@PBE with the converged LAPW + HLOs basis agrees well with the energy distribution curves from photo-electron spectroscopy for pyrite. We have also investigated the performances of several hybrid functionals, which were previously shown to be able to predict band gaps of many insulating systems with accuracy close or comparable to GW. It is shown that the hybrid functionals considered in general fail badly to describe the band structures of FeS2 polymorphs. This work indicates that accurate prediction of electronic band structure of FeS2 poses a stringent test on state-of-the-art first-principles approaches, and the G0W0 method based on semi-local approximation performs well for this difficult system if it is practiced with well-converged numerical accuracy.

Band structure, phonon spectrum, and thermoelectric properties of β-BiAs and β-BiSb monolayers

2020 ◽  
Vol 8 (2) ◽  
pp. 581-590 ◽  
Author(s):  
C. Y. Wu ◽  
L. Sun ◽  
J. C. Han ◽  
H. R. Gong
Keyword(s):  
Band Structure ◽  
Thermoelectric Properties ◽  
First Principles ◽  
Phonon Spectrum ◽  
Transport Theory ◽  
First Principles Calculation ◽  
Boltzmann Transport ◽  
Band Structures ◽  
Boltzmann Transport Theory ◽  
Phonon Spectra

First-principles calculation and Boltzmann transport theory have been combined to comparatively investigate the band structures, phonon spectra, and thermoelectric properties of both β-BiSb and β-BiAs monolayers.

scholarly journals Scattering of VHF radio waves from within an ice sheet containing the vertical-girdle-type ice fabric and anisotropic reflection boundaries

2003 ◽  
Vol 37 ◽  
pp. 305-316 ◽  
Author(s):  
Shuji Fujita ◽  
Kenichi Matsuoka ◽  
Hideo Maeno ◽  
Teruo Furukawa
Keyword(s):  
Ice Sheet ◽  
Polarization Plane ◽  
Anisotropic Scattering ◽  
Physical Structure ◽  
Antenna System ◽  
Cross Polarization ◽  
Radio Waves ◽  
Experimental Conditions ◽  
Different Types ◽  
Remote Measurements

AbstractWe studied the scattering of radio waves off strata within the ice sheet at Mizuho station, Antarctica, to determine the most plausible scattering mechanisms at this location. We measured the effects of birefringence and anisotropic scattering boundaries on the return signal using the following set of experimental conditions: (1) co-polarization and cross-polarization antenna arrangements, (2) all orientations of the antenna system, (3) 60 and 179 MHz frequencies, and (4) pulse lengths of 150–1000 ns. Analyses of the propagated radio waves suggested that the signal is dominated by anisotropic scatter-ingboundaries at 179 MHz, but effects from birefringence also occurred. At depths of 250– 750 m, the scattering was stronger when the polarization plane was along the flowline. In contrast, at depths of about 900–1500 m, scattering was stronger when the polarization plane was perpendicular to the flowline. We suggest that the scattering below about 250 m is related to a layered ice stratum of crystal-orientation fabrics with different types or different cluster strengths. Although our study was at a single site, similar remote measurements over wider regions should provide valuable information about the physical structure of this vast ice sheet.

DIRAC POINTS, TOPOLOGICAL EDGE MODES AND NONRECIPROCAL TRANSMISSION IN ONE-DIMENSIONAL METAMATERIAL-BASED COUPLED-CAVITY ARRAYS

2013 ◽  
Vol 28 (02) ◽  
pp. 1441006 ◽  
Author(s):  
VASSILIOS YANNOPAPAS
Keyword(s):  
Magnetic Field ◽  
External Magnetic Field ◽  
Band Structure ◽  
Frequency Band ◽  
Negative Phase ◽  
Band Structures ◽  
One Dimensional ◽  
Scattering Spectrum ◽  
Coupled Cavity ◽  
Nonreciprocal Transmission

We show that topological frequency band structures emerge in one-dimensional (1D) electromagnetic (EM) lattices of metamaterial components without the application of an external magnetic field. Such lattices can be cavity arrays coupled with metamaterial elements which generate alternate positive and negative-phase hopping strengths. The topological nature of the band structure manifests itself by the occurrence of Dirac points in the band structure, by the emergence of edge modes in finite arrays as well as by a nonreciprocal scattering spectrum. Specific EM designs for demonstrating the above phenomena are discussed.

scholarly journals Adjusting the band structure and defects of ZnO quantum dots via tin doping

RSC Advances ◽  
2017 ◽  
Vol 7 (19) ◽  
pp. 11345-11354 ◽  
Author(s):  
Weimin Yang ◽  
Bing Zhang ◽  
Qitu Zhang ◽  
Lixi Wang ◽  
Bo Song ◽  
...  
Keyword(s):  
Density Functional Theory ◽  
Quantum Dots ◽  
Band Structure ◽  
Density Functional ◽  
Band Structures ◽  
Functional Theory ◽  
Doped Zno ◽  
Zno Quantum Dots

The structures and band structures of Sn doped ZnO were investigated by density functional theory as well as experiment.

Formation of Bending-Wave Band Structures in Bicoupled Beam-Type Phononic Crystals

2013 ◽  
Vol 81 (1) ◽  
Author(s):  
Y. Q. Guo ◽  
D. N. Fang
Keyword(s):  
Dispersion Relation ◽  
Closed Form ◽  
Phononic Crystals ◽  
Formation Mechanisms ◽  
Wave Band ◽  
Band Structures ◽  
Bending Waves ◽  
Beam Type ◽  
Thickness Shear ◽  
Bending Wave

Beam-type phononic crystals as one kind of periodic material bear frequency bands for bending waves. For the first time, this paper presents formation mechanisms of the phase constant spectra in pass-bands of bending waves (coupled flexural and thickness-shear waves) in bicoupled beam-type phononic crystals based on the model of periodic binary beam with rigidly connected joints. Closed-form dispersion relation of bending waves in the bicoupled periodic binary beam is obtained by our proposed method of reverberation-ray matrix (MRRM), based on which the bending-wave band structures in the bicoupled binary beam phononic crystal are found to be generated from the dispersion curves of the equivalent bending waves in the unit cell due to the zone folding effect, the cut-off characteristic of thickness-shear wave mode, and the wave interference phenomenon. The ratios of band-coefficient products, the characteristic times of the unit cell and the characteristic times of the constituent beams are revealed as the three kinds of essential parameters deciding the formation of bending-wave band structures. The MRRM, the closed-form dispersion relation, the formation mechanisms, and the essential parameters for the bending-wave band structures in bicoupled binary beam phononic crystals are validated by numerical examples, all of which will promote the applications of beam-type phononic crystals for wave filtering/guiding and vibration isolation/control.

Absolute Band Gaps in Two-Dimensional Phononic Crystal Plates

2006 ◽  
Author(s):  
Je´roˆme Vasseur ◽  
Pierre A. Deymier ◽  
Bahram Djafari-Rouhani ◽  
Yan Pennec
Keyword(s):  
Band Structure ◽  
Phononic Crystal ◽  
Plate Thickness ◽  
Two Dimensional ◽  
Plane Wave Expansion ◽  
Elastic Band ◽  
Band Structures ◽  
Super Cell ◽  
Order Of Magnitude ◽  
Crystal Dispersion

The elastic band structures of two-dimensional phononic crystal plates are computed with the help of a super-cell plane wave expansion (PWE) method. These band structures strongly differ from the infinite 2D phononic crystal dispersion curves. In particular, these band structures exhibit surface modes and guided modes. The influence of the constituent materials, of the plate thickness and of the geometry of the array on the band structure is investigated. We focus more specifically on determining the thicknesses of the plate for which absolute forbidden bands exist. Namely, we show that absolute forbidden bands occur in the band structure if the thickness of the plate is of the same order of magnitude as the periodicity of the array of inclusions.

scholarly journals The role of excess Sn in Cu4Sn7S16 for modification of the band structure and a reduction in lattice thermal conductivity

2017 ◽  
Vol 5 (17) ◽  
pp. 4206-4213 ◽  
Author(s):  
Tongtong He ◽  
Naiming Lin ◽  
Zhengliang Du ◽  
Yimin Chao ◽  
Jiaolin Cui
Keyword(s):  
Thermal Conductivity ◽  
Band Structure ◽  
Lattice Thermal Conductivity ◽  
Band Structures

In this work, we have investigated the band structures of ternary Cu4Sn7+xS16 (x = 0–1.0) compounds with an excess of Sn, and examined their thermoelectric (TE) properties.

scholarly journals Comparison of Non-Parabolic Hydrodynamic Models Based On Different Band Structure Models

VLSI Design ◽  
1998 ◽  
Vol 6 (1-4) ◽  
pp. 177-180
Author(s):  
Arlynn W. Smith ◽  
Kevin F. Brennan
Keyword(s):  
Dispersion Relation ◽  
Band Structure ◽  
Energy Range ◽  
Closed Form ◽  
Power Law ◽  
Hydrodynamic Model ◽  
Wide Energy Range ◽  
Hydrodynamic Models ◽  
Wide Energy ◽  
Extended Power

This paper presents two non-parabolic hydrodynamic model formulations suitable for the simulation of inhomogeneous semiconductor devices. The first formulation uses the Kane dispersion relationship, (ℏk)2/2m = W(1+αW). The second formulation makes use of a power law, (ℏk)2/2m = xWy, for the dispersion relation. The non-parabolicity and energy range of the hydrodynamic model based on the Kane dispersion relation is limited. The power law formulation produces closed form coefficients similar to those under the parabolic band approximation but the carrier concentration can deviate. An extended power law dispersion relation is proposed to account for band structure effects, (ℏk)2/2m = xW1+yW. This dispersion relation closely matches the calculated band structure over a wide energy range and may lead to closed form coefficients for the hydrodynamic model.

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