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Weyl and Dirac semimetals in three-dimensional solids Open
Weyl and Dirac semimetals are three dimensional phases of matter with gapless\nelectronic excitations that are protected by topology and symmetry. As three\ndimensional analogs of graphene, they have generated much recent interest. Deep\nc…
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Beyond Dirac and Weyl fermions: Unconventional quasiparticles in conventional crystals Open
INTRODUCTION Condensed-matter systems have recently become a fertile ground for the discovery of fermionic particles and phenomena predicted in high-energy physics; examples include Majorana fermions, as well as Dirac and Weyl semimetals. …
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Observation of tunable band gap and anisotropic Dirac semimetal state in black phosphorus Open
Tuning the band gap of black phosphorus Most materials used in electronics are semiconductors. The sizable energy gap in their electronic structure makes it easy to turn the conduction of electricity on and off. Graphene naturally lacks th…
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Dirac cone protected by non-symmorphic symmetry and three-dimensional Dirac line node in ZrSiS Open
Materials harbouring exotic quasiparticles, such as massless Dirac and Weyl fermions, have garnered much attention from physics and material science communities due to their exceptional physical properties such as ultra-high mobility and e…
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Topological node-line semimetal in three-dimensional graphene networks Open
Graphene, a two dimensional (2D) carbon sheet, acquires many of its amazing\nproperties from the Dirac point nature of its electronic structures with\nnegligible spin-orbit coupling. Extending to 3D space, graphene networks with\nnegative …
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Evidence for Majorana bound states in an iron-based superconductor Open
An iron home for Majoranas The surface of the iron-based superconductor FeTe 0.55 Se 0.45 has been identified as a potential topological superconductor and is expected to host exotic quasiparticles called the Majorana bound states (MBSs). …
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Dirac Semimetals in Two Dimensions Open
Graphene is famous for being a host of 2D Dirac fermions. However, spin-orbit coupling introduces a small gap, so that graphene is formally a quantum spin Hall insulator. Here we present symmetry-protected 2D Dirac semimetals, which featur…
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Observation of topological superconductivity on the surface of an iron-based superconductor Open
A topological superconductor A promising path toward topological quantum computing involves exotic quasiparticles called the Majorana bound states (MBSs). MBSs have been observed in heterostructures that require careful nanofabrication, bu…
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Theoretical Discovery/Prediction: Weyl Semimetal states in the TaAs material (TaAs, NbAs, NbP, TaP) class Open
The recent discoveries of Dirac fermions in graphene and on the surface of topological insulators have ignited worldwide interest in physics and materials science. A Weyl semimetal is an unusual crystal where electrons also behave as massl…
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Phagraphene: A Low-Energy Graphene Allotrope Composed of 5–6–7 Carbon Rings with Distorted Dirac Cones Open
Using systematic evolutionary structure searching we propose a new carbon allotrope, phagraphene [fæ'græfi:n], standing for penta-hexa-hepta-graphene, because the structure is composed of 5-6-7 carbon rings. This two-dimensional (2D) carbo…
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Giant, unconventional anomalous Hall effect in the metallic frustrated magnet candidate, KV <sub>3</sub> Sb <sub>5</sub> Open
The anomalous Hall effect soars when Dirac quasiparticles meet frustrated magnetism.
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Dirac Fermions in Borophene Open
Honeycomb structures of group IV elements can host massless Dirac fermions with nontrivial Berry phases. Their potential for electronic applications has attracted great interest and spurred a broad search for new Dirac materials especially…
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Lorentz-violating type-II Dirac fermions in transition metal dichalcogenide PtTe2 Open
Topological semimetals have recently attracted extensive research interests as host materials to condensed matter physics counterparts of Dirac and Weyl fermions originally proposed in high energy physics. Although Lorentz invariance is re…
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Giant negative magnetoresistance induced by the chiral anomaly in individual Cd3As2 nanowires Open
Dirac electronic materials beyond graphene and topological insulators have recently attracted considerable attention. Cd 3 As 2 is a Dirac semimetal with linear dispersion along all three momentum directions and can be viewed as a three-di…
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The rare two-dimensional materials with Dirac cones Open
Inspired by the great development of graphene, more and more research has been conducted to seek new two-dimensional (2D) materials with Dirac cones. Although 2D Dirac materials possess many novel properties and physics, they are rare comp…
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Multiple Types of Topological Fermions in Transition Metal Silicides Open
Exotic massless fermionic excitations with nonzero Berry flux, other than the Dirac and Weyl fermions, could exist in condensed matter systems under the protection of crystalline symmetries, such as spin-1 excitations with threefold degene…
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Topological semimetals predicted from first-principles calculations Open
We have given a summary on our theoretical predictions of three kinds of topological semimetals (TSMs), namely, Dirac semimetal (DSM), Weyl semimetal (WSM) and node-line semimetal (NLSM). TSMs are new states of quantum matter, which are di…
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Failure of Nielsen-Ninomiya Theorem and Fragile Topology in Two-Dimensional Systems with Space-Time Inversion Symmetry: Application to Twisted Bilayer Graphene at Magic Angle Open
We show that the Wannier obstruction and the fragile topology of the nearly flat bands in twisted bilayer graphene at magic angle are manifestations of the nontrivial topology of two-dimensional real wave functions characterized by the Eul…
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Double Dirac Semimetals in Three Dimensions Open
We study a class of Dirac semimetals that feature an eightfold-degenerate double Dirac point. We show that 7 of the 230 space groups can host such Dirac points and argue that they all generically display linear dispersion. We introduce an …
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Chiral Anomaly as the Origin of the Planar Hall Effect in Weyl Semimetals Open
In condensed matter physics, the term "chiral anomaly" implies the violation of the separate number conservation laws of Weyl fermions of different chiralities in the presence of parallel electric and magnetic fields. One effect of the chi…
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Double-Weyl Phonons in Transition-Metal Monosilicides Open
We employed ab initio calculations to identify a class of crystalline materials of MSi (M=Fe, Co, Mn, Re, Ru) having double-Weyl points in both their acoustic and optical phonon spectra. They exhibit novel topological points termed "spin-1…
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Semi-metallic Be5C2 monolayer global minimum with quasi-planar pentacoordinate carbons and negative Poisson’s ratio Open
Designing new materials with novel topological properties and reduced dimensionality is always desirable for material innovation. Here we report the design of a two-dimensional material, namely Be 5 C 2 monolayer on the basis of density fu…
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A new form of Ca3P2 with a ring of Dirac nodes Open
We report the synthesis and crystal structure of a new high-temperature form of Ca3P2. The crystal structure was determined through Rietveld refinements of synchrotron powder x-ray diffraction data. This form of Ca3P2 has a crystal structu…
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Line of Dirac Nodes in Hyperhoneycomb Lattices Open
We propose a family of structures that have "Dirac loops," closed lines of Dirac nodes in momentum space, on which the density of states vanishes linearly with energy. Those lattices all possess the planar trigonal connectivity present in …
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Majorana Corner Modes in a High-Temperature Platform Open
We introduce two-dimensional topological insulators in proximity to high-temperature cuprate or iron-based superconductors as high-temperature platforms of Majorana Kramers pairs of zero modes. The proximity-induced pairing at the helical …
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Large nonsaturating magnetoresistance and signature of nondegenerate Dirac nodes in ZrSiS Open
Significance Topological semimetals provide the opportunity to explore the fundamental physics of relativistic particles and offer the possibility of technological applications. However, finding robust systems with a sufficiently large ran…
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Trivial and inverted Dirac bands and the emergence of quantum spin Hall states in graphene on transition-metal dichalcogenides Open
Proximity orbital and spin-orbital effects of graphene on monolayer\ntransition-metal dichalcogenides (TMDCs) are investigated from\nfirst-principles. The Dirac band structure of graphene is found to lie within\nthe semiconducting gap of T…
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Imaging Dirac-mass disorder from magnetic dopant atoms in the ferromagnetic topological insulator Cr <sub>x</sub> (Bi <sub>0.1</sub> Sb <sub>0.9</sub> ) <sub>2-x</sub> Te <sub>3</sub> Open
Significance Surface states of topological insulators (TIs) should exhibit extraordinary electronic phenomena when a ‘Dirac-mass gap’ is opened in their spectrum, typically by creating a ferromagnetic state. However, our direct visualizati…
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Three-dimensional Dirac semimetals: Design principles and predictions of new materials Open
Design principles and novel predictions of new 3D Dirac semimetals are presented, along with the context of currently known materials. Current materials include those based on a topological to trivial phase transition, such as in TlBiSe$_{…
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Transport of Topological Semimetals Open
Three-dimensional (3D) topological semimetals represent a new class of topological matters. The study of this family of materials has been at the frontiers of condensed matter physics, and many breakthroughs have been made. Several topolog…