scholarly journals Coexistence of type-II and type-IV Dirac fermions in SrAgBi

2021 ◽  
pp. 2150181
Author(s):  
Tian-Chi Ma ◽  
Jing-Nan Hu ◽  
Yuan Chen ◽  
Lei Shao ◽  
Xian-Ru Hu ◽  
...  
Keyword(s):  
High Energy Physics ◽  
Surface States ◽  
High Energy ◽  
Dirac Fermion ◽  
Dirac Fermions ◽  
Type Ii ◽  
Linear Dispersion ◽  
Space Groups ◽  
Type Iv ◽  
Poincaré Symmetry

Relativistic massless Weyl and Dirac fermions have isotropic and linear dispersion relations to maintain Poincaré symmetry, which is the most basic symmetry in high-energy physics. The situation in condensed matter physics is less constrained; only certain subgroups of Poincaré symmetry — the 230 space groups that exist in 3D lattices — need be respected. Then, the free fermionic excitations that have no high-energy analogues could exist in solid state systems. Here, We discovered a type of nonlinear Dirac fermion without high-energy analogue in SrAgBi and named it type-IV Dirac fermion. The type-IV Dirac fermion has a nonlinear dispersion relationship and is similar to the type-II Dirac fermion, which has electron pocket and hole pocket. The effective model for the type-IV Dirac fermion is also found. It is worth pointing out that there is a type-II Dirac fermion near this new Dirac fermion. So we used two models to describe the coexistence of these two Dirac fermions. Topological surface states of these two Dirac points are also calculated. We envision that our findings will stimulate researchers to study novel physics of type-IV Dirac fermions, as well as the interplay of type-II and type-IV Dirac fermions.

scholarly journals Robust edge photocurrent response on layered type II Weyl semimetal WTe2

2019 ◽  
Vol 10 (1) ◽  
Author(s):  
Qinsheng Wang ◽  
Jingchuan Zheng ◽  
Yuan He ◽  
Jin Cao ◽  
Xin Liu ◽  
...  
Keyword(s):  
Energy Harvesting ◽  
Surface States ◽  
Separation Mechanism ◽  
Current Response ◽  
Type Ii ◽  
Nonlinear Optical Effect ◽  
Linear Dispersion ◽  
Weyl Semimetal ◽  
Quantum Materials ◽  
A Charge

AbstractPhotosensing and energy harvesting based on exotic properties of quantum materials and new operation principles have great potential to break the fundamental performance limit of conventional photodetectors and solar cells. Weyl semimetals have demonstrated novel optoelectronic properties that promise potential applications in photodetection and energy harvesting arising from their gapless linear dispersion and Berry field enhanced nonlinear optical effect at the vicinity of Weyl nodes. In this work, we demonstrate robust photocurrent generation at the edge of Td-WTe2, a type-II Weyl semimetal, due to crystalline-symmetry breaking along certain crystal fracture directions and possibly enhanced by robust fermi-arc type surface states. This edge response is highly generic and arises universally in a wide class of quantum materials with similar crystal symmetries. The robust and generic edge current response provides a charge separation mechanism for photosensing and energy harvesting over broad wavelength range.

scholarly journals Fermi-crossing Type-II Dirac fermions and topological surface states in NiTe2

2020 ◽  
Vol 10 (1) ◽  
Author(s):  
Saumya Mukherjee ◽  
Sung Won Jung ◽  
Sophie F. Weber ◽  
Chunqiang Xu ◽  
Dong Qian ◽  
...  
Keyword(s):  
Surface States ◽  
Dirac Fermions ◽  
Type Ii ◽  
Topological Surface

scholarly journals Terahertz signatures of ultrafast Dirac fermion relaxation at the surface of topological insulators

2021 ◽  
Vol 6 (1) ◽  
Author(s):  
S. Kovalev ◽  
K.-J. Tielrooij ◽  
J.-C. Deinert ◽  
I. Ilyakov ◽  
N. Awari ◽  
...  
Keyword(s):  
Fermi Level ◽  
Topological Insulators ◽  
Surface States ◽  
Dirac Fermion ◽  
Dirac Fermions ◽  
Bulk Carriers ◽  
Information And Communication ◽  
Protected Surface ◽  
Saturation Effects ◽  
Conversion Efficiencies

AbstractTopologically protected surface states present rich physics and promising spintronic, optoelectronic, and photonic applications that require a proper understanding of their ultrafast carrier dynamics. Here, we investigate these dynamics in topological insulators (TIs) of the bismuth and antimony chalcogenide family, where we isolate the response of Dirac fermions at the surface from the response of bulk carriers by combining photoexcitation with below-bandgap terahertz (THz) photons and TI samples with varying Fermi level, including one sample with the Fermi level located within the bandgap. We identify distinctly faster relaxation of charge carriers in the topologically protected Dirac surface states (few hundred femtoseconds), compared to bulk carriers (few picoseconds). In agreement with such fast cooling dynamics, we observe THz harmonic generation without any saturation effects for increasing incident fields, unlike graphene which exhibits strong saturation. This opens up promising avenues for increased THz nonlinear conversion efficiencies, and high-bandwidth optoelectronic and spintronic information and communication applications.

scholarly journals The study of magnetic topological semimetals by first principles calculations

2019 ◽  
Vol 5 (1) ◽  
Author(s):  
Jinyu Zou ◽  
Zhuoran He ◽  
Gang Xu
Keyword(s):  
Surface States ◽  
Nodal Line ◽  
Future Research ◽  
Honeycomb Lattice ◽  
Space Groups ◽  
Type Iv ◽  
Fermi Arcs ◽  
Topological Quantum ◽  
Recent Developments ◽  
Topological Semimetals

Abstract Magnetic topological semimetals (TSMs) are topological quantum materials with broken time-reversal symmetry (TRS) and isolated nodal points or lines near the Fermi level. Their topological properties would typically reveal from the bulk-edge correspondence principle as nontrivial surface states such as Fermi arcs or drumhead states, etc. Depending on the degeneracies and distribution of the nodes in the crystal momentum space, TSMs are usually classified into Weyl semimetals (WSMs), Dirac semimetals (DSMs), nodal-line semimetals (NLSMs), triple-point semimetals (TPSMs), etc. In this review article, we present the recent advances of magnetic TSMs from a computational perspective. We first review the early predicted magnetic WSMs such as pyrochlore iridates and HgCr2Se4, as well as the recently proposed Heusler, Kagome layers, and honeycomb lattice WSMs. Then we discuss the recent developments of magnetic DSMs, especially CuMnAs in Type-III and EuCd2As2 in Type-IV magnetic space groups (MSGs). Then we introduce some magnetic NLSMs that are robust against spin–orbit coupling (SOC), namely Fe3GeTe2 and LaCl (LaBr). Finally, we discuss the prospects of magnetic TSMs and the interesting directions for future research.

scholarly journals Glide symmetry protected higher-order topological insulators from semimetals with butterfly-like nodal lines

2021 ◽  
Vol 7 (1) ◽  
Author(s):  
Xiaoting Zhou ◽  
Chuang-Han Hsu ◽  
Cheng-Yi Huang ◽  
Mikel Iraola ◽  
Juan L. Mañes ◽  
...  
Keyword(s):  
Topological Insulator ◽  
Topological Insulators ◽  
Surface States ◽  
Nodal Line ◽  
Higher Order ◽  
Dirac Fermion ◽  
Space Groups ◽  
Nodal Lines ◽  
Topological Semimetals ◽  
Symmetry Protected

AbstractMost topological insulators (TIs) discovered today in spinful systems can be transformed from topological semimetals (TSMs) with vanishing bulk gap via introducing the spin-orbit coupling (SOC), which manifests the intrinsic links between the gapped topological insulator phases and the gapless TSMs. Recently, we have discovered a family of TSMs in time-reversal invariant spinless systems, which host butterfly-like nodal-lines (NLs) consisting of a pair of identical concentric intersecting coplanar ellipses (CICE). In this Communication, we unveil the intrinsic link between this exotic class of nodal-line semimetals (NLSMs) and a $${{\mathbb{Z}}}_{4}$$ Z 4 = 2 topological crystalline insulator (TCI), by including substantial SOC. We demonstrate that in three space groups (i.e., Pbam (No.55), P4/mbm (No.127), and P42/mbc (No.135)), the TCI supports a fourfold Dirac fermion on the (001) surface protected by two glide symmetries, which originates from the intertwined drumhead surface states of the CICE NLs. The higher order topology is further demonstrated by the emergence of one-dimensional helical hinge states, indicating the discovery of a higher order topological insulator protected by a glide symmetry.

Labelling of non-A, non-B hepatitis infected chimpanzee hepatocytes with nuclease-gold conjugates

1984 ◽  
Vol 42 ◽  
pp. 250-251
Author(s):  
G. D. Gagne ◽  
M. F. Miller ◽  
D. A. Peterson
Keyword(s):  
Endoplasmic Reticulum ◽  
Experimental Infection ◽  
Uranyl Acetate ◽  
Type I ◽  
Cellular Injury ◽  
Type Ii ◽  
Tubular Structures ◽  
Type Iii ◽  
Type Iv ◽  
Infected Chimpanzee

Experimental infection of chimpanzees with non-A, non-B hepatitis (NANB) or with delta agent hepatitis results in the appearance of characteristic cytoplasmic alterations in the hepatocytes. These alterations include spongelike inclusions (Type I), attached convoluted membranes (Type II), tubular structures (Type III), and microtubular aggregates (Type IV) (Fig. 1). Type I, II and III structures are, by association, believed to be derived from endoplasmic reticulum and may be morphogenetically related. Type IV structures are generally observed free in the cytoplasm but sometimes in the vicinity of type III structures. It is not known whether these structures are somehow involved in the replication and/or assembly of the putative NANB virus or whether they are simply nonspecific responses to cellular injury. When treated with uranyl acetate, type I, II and III structures stain intensely as if they might contain nucleic acids. If these structures do correspond to intermediates in the replication of a virus, one might expect them to contain DNA or RNA and the present study was undertaken to explore this possibility.

The distribution and density of ciliary tufts on the siphons of Anodonta cygnea (Mollusca: Bivalvia)

1990 ◽  
Vol 48 (3) ◽  
pp. 518-519
Author(s):  
Wen-lung Wu
Keyword(s):  
Osmium Tetroxide ◽  
Internal Surface ◽  
Mechanical Stimuli ◽  
Type Ii ◽  
Sensory Receptors ◽  
Anodonta Cygnea ◽  
Type Iv ◽  
Sem Study ◽  
Inhalant Siphon ◽  
Type V

The mantle of bivalves has come entirely to enclose the laterally compressed body and the mantle margin has assumed a variety of functions, one of the pricipal ones being sensory. Ciliary tufts, which are probably sensory, have been reported from the mantle and siphons of several bivalves1∽4. Certain regions of the mantle margin are likely to be more or less, sensitive to certain stimuli than others. The inhalant siphon is likely to be particularly sensitive to both chemical and mechanical stimuli, whereas the exhalant siphon will be less sensitive to both. The distribution and density of putative sensory receptors on the in-and ex-halant siphon is compared in this paper.The excised siphons were fixed in glutaraldehyde and osmium tetroxide, the whole procedure of SEM study is recorded in Wu's thesis.Type II cilia cover the tips of tentacles, 6.13um. Type IV and type V cilia are found on the surface of tentacles. Type IV cilia are occasionally present at the tips of tentacles, 8 um long. They are the commonest type on the surface of tentacles. Type VI cilia occor in the internal surface of the inhalant siphon, but are not found on the surface of tentacles, 6.7-10um long.

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