A nonsymmorphic-symmetry-protected hourglass Weyl node, hybrid Weyl node, nodal surface, and Dirac nodal line in Pd4X (X = S, Se) compounds

2020 ◽  
Vol 22 (39) ◽  
pp. 22399-22407
Author(s):  
Weizhen Meng ◽  
Ying Liu ◽  
Xiaoming Zhang ◽  
Xuefang Dai ◽  
Guodong Liu
Keyword(s):  
Nodal Line ◽  
Nodal Surface ◽  
Topological Semimetals ◽  
Symmetry Protected

Nonsymmorphic symmetry has been proved to protect band crossings in topological semimetals/metals.

scholarly journals Glide symmetry protected higher-order topological insulators from semimetals with butterfly-like nodal lines

2021 ◽  
Vol 7 (1) ◽  
Author(s):  
Xiaoting Zhou ◽  
Chuang-Han Hsu ◽  
Cheng-Yi Huang ◽  
Mikel Iraola ◽  
Juan L. Mañes ◽  
...  
Keyword(s):  
Topological Insulator ◽  
Topological Insulators ◽  
Surface States ◽  
Nodal Line ◽  
Higher Order ◽  
Dirac Fermion ◽  
Space Groups ◽  
Nodal Lines ◽  
Topological Semimetals ◽  
Symmetry Protected

AbstractMost topological insulators (TIs) discovered today in spinful systems can be transformed from topological semimetals (TSMs) with vanishing bulk gap via introducing the spin-orbit coupling (SOC), which manifests the intrinsic links between the gapped topological insulator phases and the gapless TSMs. Recently, we have discovered a family of TSMs in time-reversal invariant spinless systems, which host butterfly-like nodal-lines (NLs) consisting of a pair of identical concentric intersecting coplanar ellipses (CICE). In this Communication, we unveil the intrinsic link between this exotic class of nodal-line semimetals (NLSMs) and a $${{\mathbb{Z}}}_{4}$$ Z 4 = 2 topological crystalline insulator (TCI), by including substantial SOC. We demonstrate that in three space groups (i.e., Pbam (No.55), P4/mbm (No.127), and P42/mbc (No.135)), the TCI supports a fourfold Dirac fermion on the (001) surface protected by two glide symmetries, which originates from the intertwined drumhead surface states of the CICE NLs. The higher order topology is further demonstrated by the emergence of one-dimensional helical hinge states, indicating the discovery of a higher order topological insulator protected by a glide symmetry.

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 Dirac nodal surfaces and nodal lines in ZrSiS

2019 ◽  
Vol 5 (5) ◽  
pp. eaau6459 ◽  
Author(s):  
B.-B. Fu ◽  
C.-J. Yi ◽  
T.-T. Zhang ◽  
M. Caputo ◽  
J.-Z. Ma ◽  
...  
Keyword(s):  
Photoemission Spectroscopy ◽  
Dirac Fermions ◽  
Fermi Surfaces ◽  
Angle Resolved Photoemission Spectroscopy ◽  
Nodal Lines ◽  
Nodal Points ◽  
Different Dimensions ◽  
Topological Semimetals ◽  
Symmetry Protected ◽  
Nodal Surfaces

Topological semimetals are characterized by symmetry-protected band crossings, which can be preserved in different dimensions in momentum space, forming zero-dimensional nodal points, one-dimensional nodal lines, or even two-dimensional nodal surfaces. Materials harboring nodal points and nodal lines have been experimentally verified, whereas experimental evidence of nodal surfaces is still lacking. Here, using angle-resolved photoemission spectroscopy (ARPES), we reveal the coexistence of Dirac nodal surfaces and nodal lines in the bulk electronic structures of ZrSiS. As compared with previous ARPES studies on ZrSiS, we obtained pure bulk states, which enable us to extract unambiguously intrinsic information of the bulk nodal surfaces and nodal lines. Our results show that the nodal lines are the only feature near the Fermi level and constitute the whole Fermi surfaces. We not only prove that the low-energy quasiparticles in ZrSiS are contributed entirely by Dirac fermions but also experimentally realize the nodal surface in topological semimetals.

Robust topological nodal lines in halide carbides

2019 ◽  
Vol 21 (36) ◽  
pp. 20262-20268 ◽  
Author(s):  
Anh Pham ◽  
Frank Klose ◽  
Sean Li
Keyword(s):  
Nodal Line ◽  
Nodal Lines ◽  
Symmetry Protected ◽  
2D And 3D

This study predicts the existence of a symmetry protected nodal line state in Y2C2I2 in both 2D and 3D.

scholarly journals Progress on topological nodal line and nodal surface

2019 ◽  
Vol 68 (22) ◽  
pp. 227101
Author(s):  
Shan-Shan Wang ◽  
Wei-Kang Wu ◽  
Sheng-Yuan Yang
Keyword(s):  
Nodal Line ◽  
Nodal Surface

scholarly journals Magnetism-induced topological transition in EuAs3

2020 ◽  
Author(s):  
Erjian Cheng ◽  
Wei Xia ◽  
Jie Xu ◽  
Chengwei Wang ◽  
Chuanying Xi ◽  
...  
Keyword(s):  
Electrical Transport ◽  
Berry Phase ◽  
Magnetic Moments ◽  
Surface States ◽  
Nodal Line ◽  
Chiral Anomaly ◽  
Topological Transition ◽  
Spin Polarized ◽  
Exotic Physics ◽  
Topological Semimetals

Abstract The nature of the interaction between magnetism and topology in magnetic topological semimetals remains mysterious, but may be expected to lead to a variety of novel physics. We present ab initio band calculations, electrical transport and angle-resolved photoemission spectroscopy (ARPES) measurements on the magnetic semimetal EuAs3, demonstrating a magnetism-induced topological transition from a topological nodal-line semimetal in the paramagnetic or the spin-polarized state to a topological massive Dirac metal in the antiferromagnetic (AFM) ground state at low temperature, featuring a pair of massive Dirac points, inverted bands and topological surface states on the (010) surface. Shubnikov-de Haas (SdH) oscillations in the AFM state identify nonzero Berry phase and a negative longitudinal magnetoresistance (n-LMR) induced by the chiral anomaly, confirming the topological nature predicted by band calculations. When magnetic moments are fully polarized by an external magnetic field, an unsaturated and extremely large magnetoresistance (XMR) of ∼ 2×105 % at 1.8 K and 28.3 T is observed, likely arising from topological protection. Consistent with band calculations for the spin-polarized state, four new bands in quantum oscillations different from those in the AFM state are discerned, of which two are topologically protected. Nodal-line structures at the Y point in the Brillouin zone (BZ) are proposed in both the spin-polarized and paramagnetic states, and the latter is proven by ARPES. Moreover, a temperature-induced Lifshitz transition accompanied by the emergence of a new band below 3 K is revealed. These results indicate that magnetic EuAs3 provides a rich platform to explore exotic physics arising from the interaction of magnetism with topology.

scholarly journals Type-II nodal line fermions in the Z2 topological semimetals AV6Sb6 ( A =K, Rb, and Cs) with a kagome bilayer

2021 ◽  
Vol 104 (24) ◽  
Author(s):  
Y. Yang ◽  
R. Wang ◽  
M.-Z. Shi ◽  
Z. Wang ◽  
Z. Xiang ◽  
...  
Keyword(s):  
Nodal Line ◽  
Type Ii ◽  
Topological Semimetals

scholarly journals Multiple Dirac nodes and symmetry protected Dirac nodal line in orthorhombic α -RhSi

2020 ◽  
Vol 102 (11) ◽  
Author(s):  
Shirin Mozaffari ◽  
Niraj Aryal ◽  
Rico Schönemann ◽  
Kuan-Wen Chen ◽  
Wenkai Zheng ◽  
...  
Keyword(s):  
Nodal Line ◽  
Symmetry Protected

scholarly journals Topological Semimetals in Square-Net Materials

2019 ◽  
Vol 49 (1) ◽  
pp. 185-206 ◽  
Author(s):  
Sebastian Klemenz ◽  
Shiming Lei ◽  
Leslie M. Schoop
Keyword(s):  
Hall Effect ◽  
Electronic Properties ◽  
Quantum Hall Effect ◽  
Quantum Hall ◽  
Nodal Line ◽  
Topological Properties ◽  
Topological Materials ◽  
Integer Quantum Hall Effect ◽  
Integer Quantum ◽  
Topological Semimetals

Many materials crystallize in structure types that feature a square net of atoms. While these compounds can exhibit many different properties, some members of this family are topological materials. Within the square-net-based topological materials, the observed properties are rich, ranging, for example, from nodal-line semimetals to a bulk half-integer quantum Hall effect. Hence, the potential for guided design of topological properties is enormous. Here we provide an overview of the crystallographic and electronic properties of these phases and show how they are linked, with the goal of understanding which square-net materials can be topological, and predict additional examples. We close the review by discussing the experimentally observed electronic properties in this family.

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