scholarly journals Fermi arc mediated entropy transport in topological semimetals

2018 ◽  
Vol 97 (19) ◽  
Author(s):  
Timothy M. McCormick ◽  
Sarah J. Watzman ◽  
Joseph P. Heremans ◽  
Nandini Trivedi
Keyword(s):  
Fermi Arc ◽  
Entropy Transport ◽  
Topological Semimetals

scholarly journals Observation and control of maximal Chern numbers in a chiral topological semimetal

Science ◽  
2020 ◽  
Vol 369 (6500) ◽  
pp. 179-183 ◽  
Author(s):  
Niels B. M. Schröter ◽  
Samuel Stolz ◽  
Kaustuv Manna ◽  
Fernando de Juan ◽  
Maia G. Vergniory ◽  
...  
Keyword(s):  
Topological Invariant ◽  
Chern Number ◽  
Linear Dispersion ◽  
Fermi Arc ◽  
Number Magnitude ◽  
Fermi Arcs ◽  
Chern Numbers ◽  
Topological Semimetals ◽  
Chiral Crystals ◽  
And Control

Topological semimetals feature protected nodal band degeneracies characterized by a topological invariant known as the Chern number (C). Nodal band crossings with linear dispersion are expected to have at most |C|=4, which sets an upper limit to the magnitude of many topological phenomena in these materials. Here, we show that the chiral crystal palladium gallium (PdGa) displays multifold band crossings, which are connected by exactly four surface Fermi arcs, thus proving that they carry the maximal Chern number magnitude of 4. By comparing two enantiomers, we observe a reversal of their Fermi-arc velocities, which demonstrates that the handedness of chiral crystals can be used to control the sign of their Chern numbers.

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 Linear and nonlinear optical responses in the chiral multifold semimetal RhSi

2020 ◽  
Vol 5 (1) ◽  
Author(s):  
Zhuoliang Ni ◽  
B. Xu ◽  
M.-Á. Sánchez-Martínez ◽  
Y. Zhang ◽  
K. Manna ◽  
...  
Keyword(s):  
Nonlinear Optical ◽  
Chemical Potential ◽  
Technological Development ◽  
Optical Responses ◽  
Chiral Magnetic Effect ◽  
Hole Band ◽  
Linear And Nonlinear ◽  
Characteristic Features ◽  
Topological Semimetals ◽  
Terahertz Emission Spectroscopy

AbstractChiral topological semimetals are materials that break both inversion and mirror symmetries. They host interesting phenomena such as the quantized circular photogalvanic effect (CPGE) and the chiral magnetic effect. In this work, we report a comprehensive theoretical and experimental analysis of the linear and nonlinear optical responses of the chiral topological semimetal RhSi, which is known to host multifold fermions. We show that the characteristic features of the optical conductivity, which display two distinct quasi-linear regimes above and below 0.4 eV, can be linked to excitations of different kinds of multifold fermions. The characteristic features of the CPGE, which displays a sign change at 0.4 eV and a large non-quantized response peak of around 160 μA/V2 at 0.7 eV, are explained by assuming that the chemical potential crosses a flat hole band at the Brillouin zone center. Our theory predicts that, in order to observe a quantized CPGE in RhSi, it is necessary to increase the chemical potential as well as the quasiparticle lifetime. More broadly, our methodology, especially the development of the broadband terahertz emission spectroscopy, could be widely applied to study photogalvanic effects in noncentrosymmetric materials and in topological insulators in a contact-less way and accelerate the technological development of efficient infrared detectors based on topological semimetals.

scholarly journals High-frequency rectifiers based on type-II Dirac fermions

2021 ◽  
Vol 12 (1) ◽  
Author(s):  
Libo Zhang ◽  
Zhiqingzi Chen ◽  
Kaixuan Zhang ◽  
Lin Wang ◽  
Huang Xu ◽  
...  
Keyword(s):  
High Frequency ◽  
Dynamic Range ◽  
High Sensitivity ◽  
High Dynamic Range ◽  
Anisotropy Ratio ◽  
Dirac Fermions ◽  
Topological States ◽  
Topological Semimetals ◽  
Polarized Surface ◽  
Symmetry Protected

AbstractThe advent of topological semimetals enables the exploitation of symmetry-protected topological phenomena and quantized transport. Here, we present homogeneous rectifiers, converting high-frequency electromagnetic energy into direct current, based on low-energy Dirac fermions of topological semimetal-NiTe2, with state-of-the-art efficiency already in the first implementation. Explicitly, these devices display room-temperature photosensitivity as high as 251 mA W−1 at 0.3 THz in an unbiased mode, with a photocurrent anisotropy ratio of 22, originating from the interplay between the spin-polarized surface and bulk states. Device performances in terms of broadband operation, high dynamic range, as well as their high sensitivity, validate the immense potential and unique advantages associated to the control of nonequilibrium gapless topological states via built-in electric field, electromagnetic polarization and symmetry breaking in topological semimetals. These findings pave the way for the exploitation of topological phase of matter for high-frequency operations in polarization-sensitive sensing, communications and imaging.

scholarly journals Observation of a singular Weyl point surrounded by charged nodal walls in PtGa

2021 ◽  
Vol 12 (1) ◽  
Author(s):  
J.-Z. Ma ◽  
Q.-S. Wu ◽  
M. Song ◽  
S.-N. Zhang ◽  
E. B. Guedes ◽  
...  
Keyword(s):  
Density Functional ◽  
Density Functional Theory Calculations ◽  
Photoemission Spectroscopy ◽  
Functional Theory ◽  
Fermi Arc ◽  
Angle Resolved Photoemission Spectroscopy ◽  
Fermi Arcs ◽  
Surface Projection ◽  
Applicable Range ◽  
Opposite Chirality

AbstractConstrained by the Nielsen-Ninomiya no-go theorem, in all so-far experimentally determined Weyl semimetals (WSMs) the Weyl points (WPs) always appear in pairs in the momentum space with no exception. As a consequence, Fermi arcs occur on surfaces which connect the projections of the WPs with opposite chiral charges. However, this situation can be circumvented in the case of unpaired WP, without relevant surface Fermi arc connecting its surface projection, appearing singularly, while its Berry curvature field is absorbed by nontrivial charged nodal walls. Here, combining angle-resolved photoemission spectroscopy with density functional theory calculations, we show experimentally that a singular Weyl point emerges in PtGa at the center of the Brillouin zone (BZ), which is surrounded by closed Weyl nodal walls located at the BZ boundaries and there is no Fermi arc connecting its surface projection. Our results reveal that nontrivial band crossings of different dimensionalities can emerge concomitantly in condensed matter, while their coexistence ensures the net topological charge of different dimensional topological objects to be zero. Our observation extends the applicable range of the original Nielsen-Ninomiya no-go theorem which was derived from zero dimensional paired WPs with opposite chirality.

Copropagating Photonic Fermi Arc Channels for Multiplexing and Dynamically Routing Topological Surface Waves

2021 ◽  
Vol 15 (4) ◽  
pp. 2000360
Author(s):  
Jinying Guo ◽  
Biao Yang ◽  
Shaojie Ma ◽  
Hsun‐Chi Chan ◽  
Guohai Situ ◽  
...  
Keyword(s):  
Surface Waves ◽  
Fermi Arc ◽  
Topological Surface

scholarly journals Topological semimetals protected by off-centered symmetries in nonsymmorphic crystals

2017 ◽  
Vol 95 (7) ◽  
Author(s):  
Bohm-Jung Yang ◽  
Troels Arnfred Bojesen ◽  
Takahiro Morimoto ◽  
Akira Furusaki
Keyword(s):  
Topological Semimetals

Electronic Structure Transformation in a Magnetized Topological Semimetal

2021 ◽  
Vol 1 ◽  
Keyword(s):  
Electronic Structure ◽  
Domain Walls ◽  
Magnetic Domain ◽  
Localized States ◽  
Structure Transformation ◽  
Nodal Lines ◽  
Topological Semimetal ◽  
Magnetic Domain Walls ◽  
Magnetic Orders ◽  
Topological Semimetals

We theoretically show that the nodal structures in topological semimetals, including Weyl points and nodal lines, can be switched by magnetic orders, accompanied by localized states at magnetic domain walls.

The Generation of Switchable Polarized Currents in Nodal Ring Semimetals Using High-Frequency Periodic Driving

2021 ◽  
Author(s):  
Pei-Hao Fu ◽  
Qianqian Lv ◽  
Xiang-Long Yu ◽  
Jun-Feng Liu ◽  
Jiansheng Wu
Keyword(s):  
High Frequency ◽  
Surface Currents ◽  
Switching Effect ◽  
Fermi Arc ◽  
Periodically Driven ◽  
Weyl Semimetal ◽  
Spin Polarized ◽  
High Frequency Electromagnetic Field ◽  
Polarized Surface ◽  
Lead Device

Abstract A nodal ring semimetal (NRSM) can be driven to a spin-polarized NRSM or a spin-polarized Weyl semimetal (SWSM) by a high-frequency electromagnetic field. We investigate the conditions in realizing these phases and propose a switchable spin-polarized currents generator based on periodically driven NRSMs. Both bulk and surface polarized currents are investigated. The polarization of bulk current is sensitive to the amplitude of the driving field and robust against the direction and polarization of the driving, the opaqueness of the lead-device interface and the misalignment between the nodal ring and the interface, which provides sufficient flexibility in manipulating the devices. Similar switchable polarized surface currents are also expected, which is contributed by the Fermi arc surface state associated with the Weyl semimetal (WSM) phases. The generation of polarized currents and the polarization switching effect offer opportunities to design periodic driving controlled topological spintronics devices based on NRSMs.

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