scholarly journals Hinge modes and surface states in second-order topological three-dimensional quantum Hall systems induced by charge density modulation

2020 ◽  
Vol 102 (12) ◽  
Author(s):  
Paweł Szumniak ◽  
Daniel Loss ◽  
Jelena Klinovaja
Keyword(s):  
Charge Density ◽  
Quantum Hall ◽  
Three Dimensional ◽  
Surface States ◽  
Second Order ◽  
Quantum Hall Systems ◽  
Density Modulation

scholarly journals DEFORMED FERMI SURFACE THEORY OF MAGNETO–ACOUSTIC RESPONSE IN MODULATED QUANTUM HALL SYSTEMS NEAR ν=1/2

1999 ◽  
Vol 13 (08) ◽  
pp. 859-868
Author(s):  
NATALIYA A. ZIMBOVSKAYA ◽  
JOSEPH L. BIRMAN
Keyword(s):  
Fermi Surface ◽  
Transport Theory ◽  
Quantum Hall ◽  
Generic Model ◽  
Fractional Quantum Hall ◽  
Quantum Hall Systems ◽  
Quantum Hall Regime ◽  
Hall Regime ◽  
Density Modulation ◽  
Dimensional Electron Gas

We develop a magneto-transport theory for the nonlocal response of a two-dimensional electron gas (2DEG) in the Fractional Quantum Hall Regime near ν=1/2 in the presence of a periodic density modulation. We introduce a new generic model of a deformed Composite Fermion–Fermi Surface (CF–FS). Our model permits us to explain recent surface acoustic wave observations of anisotropic anomalies1 in sound velocity and attenuation, such as appearance of peaks and anisotropy, which originate from contributions to the conductivity tensor due to regions of the CF–FS which are flattened by the applied modulation. The calculated magnetic field and wave vector dependence of the CF conductivity, velocity shift and attenuation agree with experiments.

scholarly journals Intrinsic coupling between spatially-separated surface Fermi-arcs in Weyl orbit quantum Hall states

2020 ◽  
Author(s):  
Shinichi Nishihaya ◽  
Masaki Uchida ◽  
Yusuke Nakazawa ◽  
Markus Kriener ◽  
Yasujiro Taguchi ◽  
...  
Keyword(s):  
Spatial Distribution ◽  
Recent Observation ◽  
Quantum Hall ◽  
Three Dimensional ◽  
Surface States ◽  
Back Gate ◽  
Fermi Arc ◽  
Quantum Hall States ◽  
Topological Semimetals ◽  
Hall States

Abstract Topological semimetals hosting bulk Weyl points and surface Fermi-arc states are expected to realize unconventional Weyl orbits, which interconnect two surface Fermi-arc states on opposite sample surfaces under magnetic fields. While the presence of Weyl orbits has been proposed to play a vital role in recent observation of quantum Hall effect even in three-dimensional topological semimetals, actual spatial distribution of the quantized surface transport has been experimentally elusive. Here, we demonstrate intrinsic coupling between two spatially-separated surface states in the Weyl orbits by measuring a dual-gate device of a Dirac semimetal film. Independent scans of top- and back-gate voltages reveal concomitant modulation of doubly-degenerate quantum Hall states, which is not possible in conventional surface orbits as in topological insulators. Our results evidencing the unique spatial distribution of Weyl orbits provide new opportunities for controlling the novel quantized transport by various means such as external fields and interface engineering.

scholarly journals Topological Photonic Media and the Possibility of Toroidal Electromagnetic Wavepackets

2019 ◽  
Vol 9 (7) ◽  
pp. 1468 ◽  
Author(s):  
Masaru Onoda
Keyword(s):  
Topological Insulators ◽  
Periodic Structures ◽  
Quantum Hall ◽  
Surface States ◽  
Simple Algorithm ◽  
Helical Surface ◽  
Surface Modes ◽  
Quantum Hall Systems ◽  
Angular Momenta ◽  
The Stability

This study aims to present a theoretical investigation of a feasible electromagnetic wavepacket with toroidal-type dual vortices. The paper begins with a discussion on geometric phases and angular momenta of electromagnetic vortices in free space and periodic structures, and introduces topological photonic media with a review on topological phenomena of electron systems in solids, such as quantum Hall systems and topological insulators. Representative simulations demonstrate both the characteristics of electromagnetic vortices in a periodic structure and of exotic boundary modes of a topological photonic crystal, on a Y-shaped waveguide configuration. Those boundary modes stem from photonic helical surface modes, i.e., a photonic analog of electronic helical surface states of topological insulators. Then, we discuss the possibility of toroidal electromagnetic wavepackets via topological photonic media, based on the dynamics of an electronic wavepacket around the boundary of a topological insulator and a correspondence relation between electronic helical surface states and photonic helical surface modes. Finally, after introducing a simple algorithm for the construction of wavepacket solutions to Maxwell’s equations with multiple types of vortices, we examine the stability of a toroidal electromagnetic wavepacket against reflection and refraction, and further discuss the transformation laws of its topological properties in the corresponding processes.

scholarly journals Boundary conductance in macroscopic bismuth crystals

2022 ◽  
Vol 13 (1) ◽  
Author(s):  
Woun Kang ◽  
Felix Spathelf ◽  
Benoît Fauqué ◽  
Yuki Fuseya ◽  
Kamran Behnia
Keyword(s):  
Quantum Hall ◽  
Three Dimensional ◽  
Surface States ◽  
Metallic Surface ◽  
Periodically Driven ◽  
Dimensional Boundary ◽  
Intimate Link ◽  
Different Shapes ◽  
The Magnetic Field ◽  
Identical Crystal

AbstractThe interface between a solid and vacuum can become electronically distinct from the bulk. This feature, encountered in the case of quantum Hall effect, has a manifestation in insulators with topologically protected metallic surface states. Non-trivial Berry curvature of the Bloch waves or periodically driven perturbation are known to generate it. Here, by studying the angle-dependent magnetoresistance in prismatic bismuth crystals of different shapes, we detect a robust surface contribution to electric conductivity when the magnetic field is aligned parallel to a two-dimensional boundary between the three-dimensional crystal and vacuum. The effect is absent in antimony, which has an identical crystal symmetry, a similar Fermi surface structure and equally ballistic carriers, but an inverted band symmetry and a topological invariant of opposite sign. Our observation confirms that the boundary interrupting the cyclotron orbits remains metallic in bismuth, which is in agreement with what was predicted by Azbel decades ago. However, the absence of the effect in antimony indicates an intimate link between band symmetry and this boundary conductance.

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