A5090760846- Topological Materials and Phenomena
- Graphene research and applications
- 2D Materials and Applications
- Iron-based superconductors research
- Rare-earth and actinide compounds
- Advanced Condensed Matter Physics
- Quantum and electron transport phenomena
- Physics of Superconductivity and Magnetism
- Magnetic and transport properties of perovskites and related materials
- Molecular Junctions and Nanostructures
- Cold Atom Physics and Bose-Einstein Condensates
- Surface and Thin Film Phenomena
- Organic and Molecular Conductors Research
- Advanced Chemical Physics Studies
- High-pressure geophysics and materials
- Magnetic Properties of Alloys
- Magnetic properties of thin films
- Chalcogenide Semiconductor Thin Films
- Inorganic Chemistry and Materials
- Advancements in Battery Materials
- Superconductivity in MgB2 and Alloys
- Quantum, superfluid, helium dynamics
- Quantum many-body systems
- Semiconductor materials and interfaces
- Quantum Mechanics and Non-Hermitian Physics
Tamkang University
2000-2025
Cheng Shiu University
2010-2022
The University of Tokyo
2017-2020
National Sun Yat-sen University
2020
Research Center for Information Technology Innovation, Academia Sinica
2020
National University of Singapore
2015-2019
Brookhaven National Laboratory
2007-2014
Japan Advanced Institute of Science and Technology
2013-2014
Institute of Physics, Academia Sinica
2013
Academia Sinica
2011
Weyl physics emerges in the laboratory fermions—massless particles with half-integer spin—were once mistakenly thought to describe neutrinos. Although not yet observed among elementary particles, fermions may exist as collective excitations so-called semimetals. These materials have an unusual band structure which linearly dispersing valence and conduction bands meet at discrete “Weyl points.” Xu et al. used photoemission spectroscopy identify TaAs a semimetal capable of hosting fermions. In...
Abstract Weyl fermions are massless chiral that play an important role in quantum field theory but have never been observed as fundamental particles. A semimetal is unusual crystal hosts quasiparticle excitations and features Fermi arcs on its surface. Such a not only provides condensed matter realization of the anomalies theories also demonstrates topological classification beyond gapped insulators. Here, we identify state transition metal monopnictide materials class. Our first-principles...
Abstract Topological semimetals can support one-dimensional Fermi lines or zero-dimensional Weyl points in momentum space, where the valence and conduction bands touch. While degeneracy are robust against any perturbation that preserves translational symmetry, nodal require protection by additional crystalline symmetries such as mirror reflection. Here we report, based on a systematic theoretical study detailed experimental characterization, existence of topological nodal-line states...
Abstract Weyl semimetals provide the realization of fermions in solid-state physics. Among all physical phenomena that are enabled by semimetals, chiral anomaly is most unusual one. Here, we report signatures magneto-transport measurements on first semimetal TaAs. We show negative magnetoresistance under parallel electric and magnetic fields, is, unlike metals whose resistivity increases an external field, observe our high mobility TaAs samples become more conductive as a field applied along...
Weyl semimetals are expected to open up new horizons in physics and materials science because they provide the first realization of fermions exhibit protected Fermi arc surface states. However, had been found be extremely rare nature. Recently, a family compounds, consisting tantalum arsenide, phosphide (TaP), niobium phosphide, was predicted as semimetal candidates. We experimentally realize state TaP. Using photoemission spectroscopy, we directly observe fermion cones nodes bulk, arcs on...
The puzzling nature of magnetic and lattice phase transitions iron pnictides is investigated via a first-principles Wannier function analysis representative parent compound LaOFeAs. A rare ferro-orbital ordering found to give rise the recently observed highly anisotropic coupling, drive both transitions--without resorting widely employed frustration or nesting picture. revealed necessity additional orbital physics leads correlated electronic structure fundamentally distinct from that...
We identify a Weyl semimetal state in an inversion breaking, stoichiometric compound strontium silicide, SrSi$_2$, with many new and novel properties that are distinct from the TaAs family. theoretically show SrSi$_2$ is even without spin-orbit coupling that, after inclusion of coupling, two fermions stick together forming exotic double fermion quadratic dispersions higher chiral topological charge 2. Moreover, we find nodes opposite charges located at different energies due to absence...
A general method is presented to unfold band structures of first-principles supercell calculations with proper spectral weight, allowing easier visualization the electronic structure and degree broken translational symmetry. The resulting unfolded contain additional rich information from Kohn-Sham orbitals, absorb factor that makes them ideal for a direct comparison angle resolved photoemission spectroscopy experiments. With negligible computational expense via use Wannier functions, this...
Weyl semimetals may open a new era in condensed matter physics because they provide the first example of fermions, realize topological classification even though system is gapless, exhibit Fermi arc surface states and demonstrate chiral anomaly other exotic quantum phenomena. So far, only known are TaAs class materials. Here, we propose existence tunable metallic state Mo$_x$W$_{1-x}$Te$_2$ via our first-principles calculations. We that 2% Mo doping sufficient to stabilize metal not at low...
Abstract The recent discovery of a Weyl semimetal in TaAs offers the first fermion observed nature and dramatically broadens classification topological phases. However, it has proven challenging to study rich transport phenomena arising from emergent fermions. series Mo x W 1− Te 2 are inversion-breaking, layered, tunable semimetals already under as promising platform for new electronics recently proposed host Type II, or strongly Lorentz-violating, Here we report at =25%. We use pump-probe...
The varying metallic antiferromagnetic correlations observed in iron-based superconductors are unified a model consisting of both itinerant electrons and localized spins. decisive factor is found to be the sensitive competition between superexchange antiferromagnetism orbital-degenerate double-exchange ferromagnetism. Our results reveal crucial role Hund's rule coupling for strongly correlated nature system suggest that closer kin manganites than cuprates terms their diverse magnetism...
The recent discovery of the first Weyl semimetal in TaAs provides observation a fermion nature and demonstrates novel type anomalous surface state, Fermi arc. Like topological insulators, bulk invariants are uniquely fixed by states sample. Here we present set distinct conditions, accessible angle-resolved photoemission spectroscopy (ARPES), each which arcs state band structure, with minimal reliance on calculation. We apply these results to NbP. For time, rigorously demonstrate nonzero...
The family of binary compounds including TaAs, TaP, NbAs, and NbP was recently discovered as the first realization Weyl semimetals. In order to develop a comprehensive description charge carriers in these semimetals, we performed systematic electronic structure calculations which reveal nature Fermi surfaces their complex interconnectivity NbP. Our work report comparative study surface topology band details all known members semimetal provide necessary building blocks for advancing our...
Members of the Mo${}_{x}$W${}_{1-x}$Te${}_{2}$ series are predicted to be Weyl semimetals, hosting type-II fermions, which have yet experimentally realized and unusual because they strongly violate Lorentz invariance. Crucially, points in this system sit above Fermi level. Here, authors show that for a cone, although not type-I if point is level, then it's necessary see band structure level observe topological arc. The also discover pump-probe angle-resolved photoemission beautifully...
A Weyl semimetal is a new state of matter that hosts fermions as quasiparticle excitations. The at zero energy correspond to points bulk-band degeneracy, called nodes, which are separated in momentum space and connected only through the crystal's boundary by an exotic Fermi arc surface state. We experimentally measure spin polarization arcs first discovered TaAs. Our data, for time, reveal arcs' spin-polarization magnitude large 80% lies completely plane surface. Moreover, we demonstrate...
Weyl semimetals may open a new era in condensed matter physics, materials science and nanotech after graphene topological insulators. We report the first atomic scale view of surface states semimetal (NbP) using scanning tunneling microscopy/spectroscopy. observe coherent quantum interference patterns that arise from scattering quasiparticles near point defects on surface. The measurements reveal electronic structure both below above chemical potential real reciprocal spaces. Moreover, maps...
A new methodology is used to design robust Weyl semimetals and identify the most ideal semimetal candidate in Ta 3 S 2 .
Differential heats of adsorption have been measured for a series alcohols, nitriles, water, and diethyl ether in H-ZSM-5 silicalite. Higher differential demonstrated that most the adsorbates had significant affinity Brønsted sites, increased with gas-phase proton adsorbate. For nitriles ether, were approximately constant up to coverage 1/site, after which values fell level on The heat formation 1:1, stoichiometric complexes slope 0.37. Heats difficult identify water alcohols since did not...
We report the experimental discovery of Adler-Bell-Jackiw chiral anomaly in a Weyl semimetal crystal.
Unfolding the band structure of a supercell to normal cell enables us investigate how symmetry breakers such as surfaces and impurities perturb cell. We generalize unfolding method, originally developed based on Wannier functions, linear combination atomic orbitals (LCAO) present general formula calculate unfolded spectral weight. The LCAO basis set is ideal for method because functions allocated each species are invariant regardless existence surface impurity. weight well defined by...
The recent discovery of the first Weyl semimetal in TaAs provides observation a fermion nature. Such topological features novel type anomalous surface state, Fermi arc, which connects pair nodes through boundary crystal. Here, we present theoretical calculations quasiparticle interference (QPI) patterns that arise from states including arcs semimetals and NbP. Most importantly, discover QPI exhibits termination points are fingerprints pattern. Our results, for time, propose universal...