Structure, elastic characteristic, ideal strengths, and phonon stability of binary uranium intermetallic UGe3 of AuCu3-type

2020 ◽  
Vol 22 (3) ◽  
pp. 1381-1391
Author(s):  
Jin-Wen Yang ◽  
Li An
Keyword(s):  
Intermetallic Compound ◽  
Brillouin Zone ◽  
Elastic Characteristic ◽  
High Symmetry ◽  
Vibration Frequencies ◽  
Characteristic Ideal

No imaginary vibration frequencies can be observed along any high symmetry directions of the Brillouin zone (BZ), confirming that the UGe3 intermetallic compound is dynamically stable.

Bulk and Surface Electronic Structure of GaN Measured Using Angle-Resolved Photoemission, Soft X-ray Emission and Soft X-ray Absorption

1996 ◽  
Vol 449 ◽  
Author(s):  
Kevin E. Smith ◽  
Sarnjeet S Dhesi ◽  
Laurent-C. Duda ◽  
Cristian B Stagarescu ◽  
J. H. Guo ◽  
...  
Keyword(s):  
Electronic Structure ◽  
Valence Band ◽  
Absorption Spectra ◽  
Conduction Band ◽  
Brillouin Zone ◽  
Emission Spectra ◽  
Partial Density ◽  
High Symmetry ◽  
X Ray ◽  
X Ray Absorption

ABSTRACTThe electronic structure of thin film wurtzite GaN has been studied using a combination of angle resolved photoemission, soft x-ray absorption and soft x-ray emission spectroscopies. We have measured the bulk valence and conduction band partial density of states by recording Ga L- and N K- x-ray emission and absorption spectra. We compare the x-ray spectra to a recent ab initio calculation and find good overall agreement. The x-ray emission spectra reveal that the top of the valence band is dominated by N 2p states, while the x-ray absorption spectra show the bottom of the conduction band as a mixture of Ga 4s and N 2p states, again in good agreement with theory. However, due to strong dipole selection rules we can also identify weak hybridization between Ga 4s- and N 2p-states in the valence band. Furthermore, a component to the N K-emission appears at approximately 19.5 eV below the valence band maximum and can be identified as due to hybridization between N 2p and Ga 3d states. We report preliminary results of a study of the full dispersion of the bulk valence band states along high symmetry directions of the bulk Brillouin zone as measured using angle resolved photoemission. Finally, we tentatively identify a non-dispersive state at the top of the valence band in parts of the Brillouin zone as a surface state.

scholarly journals A supervised learning algorithm for interacting topological insulators based on local curvature

2021 ◽  
Vol 11 (3) ◽  
Author(s):  
Paolo Molignini ◽  
Antonio Zegarra ◽  
Everard van Nieuwenburg ◽  
Ramasubramanian Chitra ◽  
Wei Chen
Keyword(s):  
Brillouin Zone ◽  
Topological Insulators ◽  
Learning Algorithm ◽  
Supervised Machine Learning ◽  
Curvature Function ◽  
High Symmetry ◽  
Topological Order ◽  
Generic Properties ◽  
Topological Quantum ◽  
Numerical Effort

Topological order in solid state systems is often calculated from the integration of an appropriate curvature function over the entire Brillouin zone. At topological phase transitions where the single particle spectral gap closes, the curvature function diverges and changes sign at certain high symmetry points in the Brillouin zone. These generic properties suggest the introduction of a supervised machine learning scheme that uses only the curvature function at the high symmetry points as input data. { We apply this scheme to a variety of interacting topological insulators in different dimensions and symmetry classes. We demonstrate that an artificial neural network trained with the noninteracting data can accurately predict all topological phases in the interacting cases with very little numerical effort.} Intriguingly, the method uncovers a ubiquitous interaction-induced topological quantum multicriticality in the examples studied.

Multiple fermions in MoP

2019 ◽  
Vol 33 (24) ◽  
pp. 1950293
Author(s):  
Jian-Peng Sun ◽  
Qing Ji ◽  
Yuan Li ◽  
Zhigang Song
Keyword(s):  
Brillouin Zone ◽  
Mirror Symmetry ◽  
Surface States ◽  
First Principles Calculation ◽  
Mirror Plane ◽  
High Symmetry ◽  
Fermi Surfaces ◽  
Topological Semimetal ◽  
New Type ◽  
Physical Phenomena

Based on the first-principles calculation, we report that the WC-type MoP is a new type of topological semimetal. It can host Weyl semimetal phase with six pairs of Weyl points (WPs) in the first whole Brillouin zone (BZ). In the absence of spin-orbit coupling (SOC), band inversion forms a gapless nodal ring protected by horizontal mirror symmetry [Formula: see text]. The strong SOC in MoP makes the nodal ring fully gapped in the mirror plane, and generates multiple WPs away from the plane. As one hallmark of Weyl semimetals, the unique Fermi arcs are also observed by calculating the projected surface states and Fermi surfaces. Besides the above prodigious features, it also possess an additional four pairs of massless fermions with triply degenerate points (TDPs) in the vicinity of the Fermi level. Each TDP is a band crossing between degenerate and non-degenerate bands along the high-symmetry line in the Brillouin zone, and is protected by crystalline symmetries. Such new type of topological semimetal realizes multiple fermions states and further provides a fancy platform to study emergent physical phenomena.

scholarly journals Band structure and gaps of triangular graphene superlattices

2010 ◽  
Vol 368 (1932) ◽  
pp. 5391-5402 ◽  
Author(s):  
F. Guinea ◽  
Tony Low
Keyword(s):  
Band Structure ◽  
Brillouin Zone ◽  
High Symmetry ◽  
Long Wavelength ◽  
General Properties ◽  
Magnetic Superlattices

The general properties of long wavelength triangular graphene superlattices are studied. It is shown that Dirac points with and without gaps can arise at a number of high-symmetry points of the Brillouin zone. The existence of gaps can lead to insulating behaviour at commensurate fillings. Strain and magnetic superlattices are also discussed.

scholarly journals Edge states of Floquet–Dirac semimetal in a laser-driven semiconductor quantum-well

2021 ◽  
Vol 11 (1) ◽  
Author(s):  
Boyuan Zhang ◽  
Nobuya Maeshima ◽  
Ken-ichi Hino
Keyword(s):  
Boundary Condition ◽  
Quantum Well ◽  
Brillouin Zone ◽  
Stark Effect ◽  
Edge State ◽  
High Symmetry ◽  
Edge States ◽  
Wide Range ◽  
Semiconductor Quantum Well ◽  
Topological States

AbstractBand crossings observed in a wide range of condensed matter systems are recognized as a key to understand low-energy fermionic excitations that behave as massless Dirac particles. Despite rapid progress in this field, the exploration of non-equilibrium topological states remains scarce and it has potential ability of providing a new platform to create unexpected massless Dirac states. Here we show that in a semiconductor quantum-well driven by a cw-laser with linear polarization, the optical Stark effect conducts bulk-band crossing, and the resulting Floquet-Dirac semimetallic phase supports an unconventional edge state in the projected one-dimensional Brillouin zone under a boundary condition that an electron is confined in the direction perpendicular to that of the laser polarization. Further, we reveal that this edge state mediates a transition between topological and non-topological edge states that is caused by tuning the laser intensity. We also show that the properties of the edge states are strikingly changed under a different boundary condition. It is found that such difference originates from that nearly fourfold-degenerate points exist in a certain intermediate region of the bulk Brillouin zone between high-symmetry points.

scholarly journals Review, Role of L12 Modified (Al1−xMex)3Ti Intermetallic Compounds on Heterogeneous Nucleation of Alpha Aluminum Grains

2020 ◽  
Vol 326 ◽  
pp. 06008
Author(s):  
Yoshimi Watanabe
Keyword(s):  
Intermetallic Compound ◽  
Intermetallic Compounds ◽  
Heterogeneous Nucleation ◽  
Nucleation Site ◽  
High Symmetry ◽  
Cast Aluminum ◽  
Heterogeneous Nucleation Site ◽  
Lattice Constants ◽  
Refining Performance

Al3Ti intermetallic compound with the tetragonal D022 structure undergoes a phase transformation to the high-symmetry L12 cubic structure by addition of third elements, Me. The lattice constants of some L12 modified (Al1−xMex)3Ti intermetallic compounds are closed to that of alpha aluminum. Therefore, it is expected that the addition of L12 modified (Al1−xMex)3Ti intermetallic compound particles show good grain refining performance of cast aluminum. In this paper, our recent results on novel refines containing heterogeneous nucleation site particles of L12 modified (Al1−xMex)3Ti intermetallic compounds have been reviewed.

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