scholarly journals Vortex Dynamics of Charge Carriers in the Quasi-Relativistic Graphene Model: High-Energy k → · p → Approximation

Symmetry ◽  
2020 ◽  
Vol 12 (2) ◽  
pp. 261 ◽  
Author(s):  
Halina Grushevskaya ◽  
George Krylov
Keyword(s):  
Band Structure ◽  
Cyclic Group ◽  
Vortex Dynamics ◽  
Mass Term ◽  
High Energy ◽  
Charge Carriers ◽  
Gauge Fields ◽  
Hamiltonian Approach ◽  
Relativistic Model

Within the earlier developed high-energy- k → · p → -Hamiltonian approach to describe graphene-like materials, the simulations of non-Abelian Zak phases and band structure of the quasi-relativistic graphene model with a number of flavors N = 3 have been performed in approximations with and without gauge fields (flavors). It has been shown that a Zak-phases set for non-Abelian Majorana-like excitations (modes) in Dirac valleys of the quasi-relativistic graphene model is the cyclic group Z 12 . This group is deformed into Z 8 at sufficiently high momenta due to deconfinement of the modes. Since the deconfinement removes the degeneracy of the eightfolding valleys, Weyl nodes and antinodes emerge. We offer that a Majorana-like mass term of the quasi-relativistic model affects the graphene band structure in the following way. Firstly, the inverse symmetry emerges in the graphene model with Majorana-like mass term, and secondly the mass term shifts the location of Weyl nodes and antinodes into the region of higher energies.

scholarly journals Polarization in Quasirelativistic Graphene Model with Topologically Non-Trivial Charge Carriers

2021 ◽  
Vol 4 (1) ◽  
pp. 1-15
Author(s):  
Halina Grushevskaya ◽  
George Krylov
Keyword(s):  
Band Structure ◽  
Spatial Dispersion ◽  
Low Frequency ◽  
Mass Term ◽  
High Energy ◽  
Charge Carriers ◽  
Gauge Fields ◽  
Complex Conductivity ◽  
Hamiltonian Approach ◽  
Majorana Mass

Within the earlier developed high-energy-k→·p→-Hamiltonian approach to describe graphene-like materials, the simulations of band structure, non-Abelian Zak phases and the complex conductivity of graphene have been performed. The quasi-relativistic graphene model with a number of flavors (gauge fields) NF=3 in two approximations (with and without a pseudo-Majorana mass term) has been utilized as a ground for the simulations. It has been shown that Zak-phases set for the non-Abelian Majorana-like excitations (modes) in graphene represent the cyclic Z12 and this group is deformed into a smaller one Z8 at sufficiently high momenta due to a deconfinement of the modes. Simulations of complex longitudinal low-frequency conductivity have been performed with a focus on effects of spatial dispersion. A spatial periodic polarization in the graphene models with the pseudo Majorana charge carriers is offered.

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.

Electronic structure, phonons and optical propertiesof baryte type scintillators TlXO4 (X=Cl, Br)

2021 ◽  
Author(s):  
Supratik Mukherjee ◽  
Aiswarya T ◽  
Subrata Mondal ◽  
Ganapathy Vaitheeswaran
Keyword(s):  
Band Structure ◽  
High Performance ◽  
High Energy Physics ◽  
Electronic Band Structure ◽  
Blue Shift ◽  
High Energy ◽  
Electronic Band ◽  
Nuclear Security ◽  
A Charge ◽  
Physics Experiments

Abstract This article thoroughly addresses the structural, mechanical, vibrational, electronic band structure and the optical properties of the unexplored thallous perchlorate and perbromate from ab-initio calculations. The zone centered vibrational phonon frequencies shows, there is a blue shift in the mid and high frequency range from Cl → Br due to change in mass and force constant with respect to oxygen atom. From the band structure it is clear that the top of the valence band is due to thallium s states, whereas the bottom of the conduction band is due to halogen s and oxygen p states, showing similar magnitude of dispersion and exhibits a charge transfer character. These characteristics and the band gap obtained are consistent with that of a favourable scintillators. Our findings deliver directions for the design of efficient TlXO4 based scintillators with high performance which are desirable for distinct applications such as medical imaging, high energy physics experiments, nuclear security.

A first-principles study of the effects of different Al constituents on Ga1−xAlxN nanowires

2016 ◽  
Vol 30 (30) ◽  
pp. 1650217 ◽  
Author(s):  
Sihao Xia ◽  
Lei Liu ◽  
Yike Kong ◽  
Honggang Wang ◽  
Meishan Wang
Keyword(s):  
Optical Properties ◽  
Band Structure ◽  
Plane Wave ◽  
First Principles ◽  
Formation Energy ◽  
High Energy ◽  
Dielectric Constants ◽  
Interesting Phenomenon ◽  
Densities Of States ◽  
Static Dielectric Constants

In order to investigate the influences of different Al constituents on Ga[Formula: see text]Al[Formula: see text]N nanowires, the formation energy, stability, band structure, densities of states and optical properties of Ga[Formula: see text]Al[Formula: see text]N nanowires with different Al constituents are calculated using first-principles plane-wave ultrasoft pseudopotential method. Results show that Ga[Formula: see text]Al[Formula: see text]N nanowires become more stable with increasing Al constituent. Bandgap of Ga[Formula: see text]Al[Formula: see text]N nanowires increases as the Al constituent increases but with a lower amplification compared with bulk Ga[Formula: see text]Al[Formula: see text]N. The peaks of static dielectric constants show a decreasing trend and move towards high-energy side as Al constituent increases. The absorption of Ga[Formula: see text]Al[Formula: see text]N nanowires shows an interesting phenomenon that it firstly increases and then decreases slightly as the Al constituent increases. Reflectivity of Ga[Formula: see text]Al[Formula: see text]N nanowires is much smaller than that of the bulk. The optical properties of Ga[Formula: see text]Al[Formula: see text]N nanowires show a blueshift effect as Al composition increases. According to these calculations, it is found that Ga[Formula: see text]Al[Formula: see text]N nanowires are appropriate to be applied into photoelectric detecting materials by adjusting the Al constituent of Ga[Formula: see text]Al[Formula: see text]N nanowires.

SUPERSTRUCTURE FORMATION AND X-RAY PHOTOEMISSION PROPERTIES OF THE TlTiOPO4 SURFACE

2004 ◽  
Vol 11 (02) ◽  
pp. 191-198 ◽  
Author(s):  
V. V. ATUCHIN ◽  
L. D. POKROVSKY ◽  
V. G. KESLER ◽  
N. YU. MAKLAKOVA ◽  
V. I. VORONKOVA ◽  
...  
Keyword(s):  
Electronic Structure ◽  
Binding Energy ◽  
Electron Diffraction ◽  
Band Structure ◽  
High Energy ◽  
Photoemission Spectroscopy ◽  
High Energy Electron ◽  
Valence Band Structure ◽  
X Ray ◽  
Core Level Binding Energy

X-ray photoemission spectroscopy (XPS) measurements have been executed for TlTiOPO 4 to elucidate the general features in the electronic structure of the KTiOPO 4 family compounds. The peculiarities of the valence band structure have been discussed for the crystals. The persistence of core level binding energy differences O 1s–P 2p and O 1s–Ti 2p 3/2 has been detected in TlTiOPO 4 and KTiOPO 4, which relates well with the constancy of averaged P – O and Ti – O chemical bond lengths in this crystal family. The superstructure ordering of the TlTiOPO 4 surface subjected to polishing and annealing has been detected by reflectance high energy electron diffraction (RHEED). From comparison of surface crystallographic properties of TlTiOPO 4 and KTiOPO 4, the most typical superstructure indices have been revealed.

scholarly journals An introduction to spontaneous symmetry breaking

2019 ◽  
Author(s):  
Aron Beekman ◽  
Louk Rademaker ◽  
Jasper van Wezel
Keyword(s):  
Symmetry Breaking ◽  
Spontaneous Symmetry Breaking ◽  
Condensed Matter ◽  
Topological Defects ◽  
High Energy ◽  
Quantum Corrections ◽  
Gauge Fields ◽  
Singular Limits ◽  
Definition Of ◽  
Goldstone Modes

Perhaps the most important aspect of symmetry in physics is the idea that a state does not need to have the same symmetries as the theory that describes it. This phenomenon is known as spontaneous symmetry breaking. In these lecture notes, starting from a careful definition of symmetry in physics, we introduce symmetry breaking and its consequences. Emphasis is placed on the physics of singular limits, showing the reality of symmetry breaking even in small-sized systems. Topics covered include Nambu-Goldstone modes, quantum corrections, phase transitions, topological defects and gauge fields. We provide many examples from both high energy and condensed matter physics. These notes are suitable for graduate students.

scholarly journals Magnetic and Optical Field Multi-Assisted Li-O2 Batteries with Self-Regulated Charge and Discharge

2020 ◽  
Author(s):  
Xiao-Xue Wang ◽  
De-Hui Guan ◽  
Fei Li ◽  
Ma-Lin Li ◽  
Li-Jun Zheng ◽  
...  
Keyword(s):  
High Performance ◽  
High Energy ◽  
Optical Field ◽  
Charge Carriers ◽  
Photogenerated Electrons ◽  
Charge Potential ◽  
Important Direction ◽  
Low Charge ◽  
Nio Nanosheets ◽  
Good Cycling Stability

Abstract The photo-assisted lithium-oxygen (Li-O2) system emerged as an important direction for future development by effectively reducing the large overpotential in Li-O2 batteries. However, the advancement is greatly hindered by the rapidly recombined photoexcited electrons and holes upon the discharging and charging processes. Herein, we make a breakthrough in overcoming these challenges by developing a new magnetic and optical field multi-assisted Li-O2 battery with 3D porous NiO nanosheets on the Ni foam (NiO/FNi) as a photoelectrode. Under illumination, the photogenerated electrons and holes of the NiO/FNi photoelectrode play a key role in reducing the overpotential during discharging and charging, respectively. By introducing the external magnetic field, the Lorentz force acts oppositely on the photogenerated electrons and holes, suppressing the recombination of charge carriers. The magnetic and optical field multi-assisted Li-O2 battery achieves an ultra-low charge potential of 2.73 V, a high energy efficiency of 96.7%, as well as a good cycling stability of 200 h. This external magnetic and optical field multi-assisted technology paves a new way of developing high-performance Li-O2 batteries and other energy storage systems.

Sign in / Sign up

Export Citation Format

Share Document