QuanSheng Wu

Three-dimensional Dirac semimetal and quantum transport in Cd3As2

Based on the first-principles calculations, we recover the silent topological nature of Cd3As2, a well known semiconductor with high carrier mobility. We find that it is a symmetry-protected topological semimetal with a single pair of three-dimensional (3D) Dirac points in the bulk and nontrivial Fermi arcs on the surfaces. It can be driven into a topological insulator and a Weyl semimetal state by symmetry breaking, or into a quantum spin Hall insulator with a gap more than 100 meV by reducing dimensionality. We propose that the 3D Dirac cones in the bulk of Cd3As2 can support sizable linear quantum magnetoresistance even up to room temperature.

Nodal-chain metals

The band theory of solids is arguably the most successful theory of condensed-matter physics, providing a description of the electronic energy levels in various materials. Electronic wavefunctions obtained from the band theory enable a topological characterization of metals for which the electronic spectrum may host robust, topologically protected, fermionic quasiparticles. Many of these quasiparticles are analogues of the elementary particles of the Standard Model, but others do not have a counterpart in relativistic high-energy theories. A complete list of possible quasiparticles in solids is lacking, even in the non-interacting case. Here we describe the possible existence of a hitherto unrecognized type of fermionic excitation in metals. This excitation forms a nodal chain—a chain of connected loops in momentum space—along which conduction and valence bands touch. We prove that the nodal chain is topologically distinct from previously reported excitations. We discuss the symmetry requirements for the appearance of this excitation and predict that it is realized in an existing material, iridium tetrafluoride (IrF4), as well as in other compounds of this class of materials. Using IrF4 as an example, we provide a discussion of the topological surface states associated with the nodal chain. We argue that the presence of the nodal-chain fermions will result in anomalous magnetotransport properties, distinct from those of materials exhibiting previously known excitations.

Triple Point Topological Metals

Quasiparticles with no direct analogs in the standard model have been recently revealed in experiments. Researchers theoretically analyze the physical properties of triple point fermions, which can be thought of as a melding of Dirac and Weyl fermions.

Observation of large topologically trivial Fermi arcs in the candidate type-II Weyl semimetal WT e 2

The authors present here several advances towards a comprehensive understanding of WTe

Fermi Arcs and Their Topological Character in the Candidate Type-II Weyl Semimetal MoTe 2

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Topological Phases in InAs_{1-x}Sb_{x}: From Novel Topological Semimetal to Majorana Wire.

. Using microfocus laser ARPES, they resolve for the first time the distinct electronic structure of both inequivalent top and bottom (001) surfaces of WTe

Quasiparticle interference of surface states in the type-II Weyl semimetal WTe2

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Hidden Weyl Points in Centrosymmetric Paramagnetic Metals

. Moreover, they demonstrate for the first time the presence of large surface state Fermi arcs on both surfaces. Using surface electronic structure calculations, they further demonstrate that these Fermi arcs are topologically trivial and that their existence is independent of the presence of type-II Weyl points in the bulk band structure. Contrary to common belief, the observation of surface state Fermi arcs is thus not suitable to robustly identify a type-II Weyl semimetal. Finally, the authors use the observation of Fermi arcs and distinct top and bottom surfaces to clarify the controversial bulk electronic structure of WTe

Experimental signatures of the inverted phase in InAs/GaSb coupled quantum wells

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Impact of strain on the electronic properties of InAs/GaSb quantum well systems

. They show that the bulk Fermi surface is formed by three-dimensional electron and hole pockets with areas that are found to be in good agreement with transport experiments, with the exception of small hole pockets that have not been observed in quantum oscillation experiments.