scholarly journals Discovery of topological Weyl fermion lines and drumhead surface states in a room temperature magnet

Science ◽  
2019 ◽  
Vol 365 (6459) ◽  
pp. 1278-1281 ◽  
Author(s):  
Ilya Belopolski ◽  
Kaustuv Manna ◽  
Daniel S. Sanchez ◽  
Guoqing Chang ◽  
Benedikt Ernst ◽  
...  
Keyword(s):  
Room Temperature ◽  
Surface States ◽  
Photoemission Spectroscopy ◽  
Topological Invariants ◽  
Fermion Line ◽  
Berry Curvature ◽  
Quantum Matter ◽  
Interacting Electrons ◽  
Strongly Interacting Electrons ◽  
Weyl Fermion

Topological matter is known to exhibit unconventional surface states and anomalous transport owing to unusual bulk electronic topology. In this study, we use photoemission spectroscopy and quantum transport to elucidate the topology of the room temperature magnet Co2MnGa. We observe sharp bulk Weyl fermion line dispersions indicative of nontrivial topological invariants present in the magnetic phase. On the surface of the magnet, we observe electronic wave functions that take the form of drumheads, enabling us to directly visualize the crucial components of the bulk-boundary topological correspondence. By considering the Berry curvature field associated with the observed topological Weyl fermion lines, we quantitatively account for the giant anomalous Hall response observed in this magnet. Our experimental results suggest a rich interplay of strongly interacting electrons and topology in quantum matter.

BULK AND SURFACE ELECTRONIC STATES OF ORDERED Cu3Au(001): AN ANGLE-RESOLVED PHOTOEMISSION INVESTIGATION

1996 ◽  
Vol 03 (05n06) ◽  
pp. 1749-1761 ◽  
Author(s):  
S. LÖBUS ◽  
R. COURTHS ◽  
S. HALILOV ◽  
H. GOLLISCH ◽  
R. FEDER
Keyword(s):  
Room Temperature ◽  
Surface States ◽  
Structure Calculation ◽  
Photoemission Spectroscopy ◽  
Surface Electronic Structure ◽  
Downward Shift ◽  
Step Model ◽  
One Step ◽  
Ultraviolet Photoemission Spectroscopy ◽  
Model Formalism

We have performed an angle-resolved ultraviolet photoemission spectroscopy (ARUPS) investigation of ordered Cu 3Au(001) at room temperature using He resonance and synchrotron radiation. The positions of upper Cu -like bulk bands near the center Γ of the bulk Brillouin zone (BZ) and the dispersion of the upper sp band along the A line have been determined using bulk-sensitive photon energies 10 eV≤hν≥15 eV. Except for a downward shift, the calculated bulk bands are in excellent agreement with experiment. Around the centers [Formula: see text] of the surface BZ, we have identified three new surface states in the energy region of the Au-like states and several surface-sensitive features in the Cu -like region below the known surface state on top of the Cu-like bulk d bands. These states strongly contribute to the ARUPS spectra for hν≥20 eV. The wealth of surface features found is in overall agreement with a recent surface electronic structure calculation [S. Halilov, H. Gollisch, E. Tamura and R. Feder, J. Phys.: Condens. Matter5, 4711 (1993)]. More detailed information is obtained by comparing the experimental spectra with theoretical ones calculated by a relativistic one-step model formalism.

Photoemission and Cathodoluminescence of Doped Lithium Tetraborate Crystals Being Developed for Neutron Detection

2011 ◽  
Vol 1341 ◽  
Author(s):  
Christina L. Dugan ◽  
Robert L. Hengehold ◽  
Stephen R. McHale ◽  
Yaroslav Losovyj ◽  
John W. McClory ◽  
...  
Keyword(s):  
Synchrotron Radiation ◽  
Energy Level ◽  
Room Temperature ◽  
Level Structure ◽  
Surface States ◽  
Photoemission Spectroscopy ◽  
Lithium Tetraborate ◽  
Energy Level Structure ◽  
Exciton Emission ◽  
Mn Doped

ABSTRACTPhotoemission spectroscopy using synchrotron radiation was used to determine the energy level structure of Mn doped Li2B4O7crystals. Photoemission studies provided evidence of Mn in the bulk crystal at 47.2 eV. Valence band analysis provided the presence of surface states but no acceptor sites. Cathodoluminescence studies were also made on undoped and Mn doped Li2B4O7using various beam energies from 5 to 10 KeV at room temperature. Self trapped exciton emission states are evident in the undoped and Mn doped Li2B4O7 sample ranging in energies from 3.1 to 4.1 eV.

scholarly journals Experimental discovery of a topological Weyl semimetal state in TaP

2015 ◽  
Vol 1 (10) ◽  
pp. e1501092 ◽  
Author(s):  
Su-Yang Xu ◽  
Ilya Belopolski ◽  
Daniel S. Sanchez ◽  
Chenglong Zhang ◽  
Guoqing Chang ◽  
...  
Keyword(s):  
Materials Science ◽  
Surface States ◽  
Photoemission Spectroscopy ◽  
New Horizons ◽  
Weyl Semimetal ◽  
Fermi Arcs ◽  
Experimental Discovery ◽  
Boundary Correspondence ◽  
First Time ◽  
Weyl Fermion

Weyl semimetals are expected to open up new horizons in physics and materials science because they provide the first realization of Weyl fermions and exhibit protected Fermi arc surface states. However, they had been found to be extremely rare in nature. Recently, a family of compounds, consisting of tantalum arsenide, tantalum phosphide (TaP), niobium arsenide, and niobium phosphide, was predicted as a Weyl semimetal candidates. We experimentally realize a Weyl semimetal state in TaP. Using photoemission spectroscopy, we directly observe the Weyl fermion cones and nodes in the bulk, and the Fermi arcs on the surface. Moreover, we find that the surface states show an unexpectedly rich structure, including both topological Fermi arcs and several topologically trivial closed contours in the vicinity of the Weyl points, which provides a promising platform to study the interplay between topological and trivial surface states on a Weyl semimetal’s surface. We directly demonstrate the bulk-boundary correspondence and establish the topologically nontrivial nature of the Weyl semimetal state in TaP, by resolving the net number of chiral edge modes on a closed path that encloses the Weyl node. This also provides, for the first time, an experimentally practical approach to demonstrating a bulk Weyl fermion from a surface state dispersion measured in photoemission.

Novel topological end modes and breaking of bulk boundary correspondence in skin-effect absent superconductive chain

2021 ◽  
Author(s):  
Huan-Yu Wang ◽  
Wu-Ming Liu
Keyword(s):  
Skin Effect ◽  
Open Quantum Systems ◽  
Quantum Systems ◽  
Topological Invariants ◽  
Quantum Matter ◽  
Topological Quantum ◽  
Boundary Correspondence ◽  
Quantum Chain ◽  
New Type ◽  
Majorana Modes

Abstract Topological nontrivial systems feature isolated gapless edge modes, and play a key role in advancing our understanding of quantum matter. A most profound way to characterize edge modes above is through bulk topological invariants, which is known as bulk boundary correspondence. Recent studies on non-Hermitian physics have pronounced the broken bulk-boundary correspondence with the presence of skin effect. Here, we propose a new type of fermionic topological edge modes η, satisfying η+= iη,η2=-i. Remarkably, we demonstrate that for both two cases: superconductive chain with purely η modes and quantum chain with η, Majorana modes γ on different ends, fermion parity can be well defined. Interestingly, for the latter case, broken bulk boundary correspondence is observed despite the absence of skin effects . The phenomenon above is unique to open quantum systems. For the junction with both η,γ modes, the current will not remain sinusoid form but decay exponentially. The exchange of η modes obeys the rules of non-abelian statistics, and can find its applications in topological quantum computing.

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