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

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.

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The study of magnetic topological semimetals by first principles calculations

npj Computational Materials ◽

10.1038/s41524-019-0237-5 ◽

2019 ◽

Vol 5 (1) ◽

Cited By ~ 11

Author(s):

Jinyu Zou ◽

Zhuoran He ◽

Gang Xu

Keyword(s):

Surface States ◽

Nodal Line ◽

Future Research ◽

Honeycomb Lattice ◽

Space Groups ◽

Type Iv ◽

Fermi Arcs ◽

Topological Quantum ◽

Recent Developments ◽

Topological Semimetals

Abstract Magnetic topological semimetals (TSMs) are topological quantum materials with broken time-reversal symmetry (TRS) and isolated nodal points or lines near the Fermi level. Their topological properties would typically reveal from the bulk-edge correspondence principle as nontrivial surface states such as Fermi arcs or drumhead states, etc. Depending on the degeneracies and distribution of the nodes in the crystal momentum space, TSMs are usually classified into Weyl semimetals (WSMs), Dirac semimetals (DSMs), nodal-line semimetals (NLSMs), triple-point semimetals (TPSMs), etc. In this review article, we present the recent advances of magnetic TSMs from a computational perspective. We first review the early predicted magnetic WSMs such as pyrochlore iridates and HgCr2Se4, as well as the recently proposed Heusler, Kagome layers, and honeycomb lattice WSMs. Then we discuss the recent developments of magnetic DSMs, especially CuMnAs in Type-III and EuCd2As2 in Type-IV magnetic space groups (MSGs). Then we introduce some magnetic NLSMs that are robust against spin–orbit coupling (SOC), namely Fe3GeTe2 and LaCl (LaBr). Finally, we discuss the prospects of magnetic TSMs and the interesting directions for future research.

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Topological semimetal in honeycomb lattice LnSI

Proceedings of the National Academy of Sciences ◽

10.1073/pnas.1713261114 ◽

2017 ◽

Vol 114 (40) ◽

pp. 10596-10600 ◽

Cited By ~ 13

Author(s):

Simin Nie ◽

Gang Xu ◽

Fritz B. Prinz ◽

Shou-cheng Zhang

Keyword(s):

Condensed Matter ◽

Surface States ◽

Nodal Line ◽

Honeycomb Lattice ◽

Nodal Lines ◽

Weyl Semimetal ◽

The Standard Model ◽

Weyl Semimetals ◽

Topological Semimetals ◽

The Right

Recognized as elementary particles in the standard model, Weyl fermions in condensed matter have received growing attention. However, most of the previously reported Weyl semimetals exhibit rather complicated electronic structures that, in turn, may have raised questions regarding the underlying physics. Here, we report promising topological phases that can be realized in specific honeycomb lattices, including ideal Weyl semimetal structures, 3D strong topological insulators, and nodal-line semimetal configurations. In particular, we highlight a semimetal featuring both Weyl nodes and nodal lines. Guided by this model, we showed that GdSI, the long-perceived ideal Weyl semimetal, has two pairs of Weyl nodes residing at the Fermi level and that LuSI (YSI) is a 3D strong topological insulator with the right-handed helical surface states. Our work provides a mechanism to study topological semimetals and proposes a platform for exploring the physics of Weyl semimetals as well as related device designs.

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Double-bowl state in photonic Dirac nodal line semimetal

Light Science & Applications ◽

10.1038/s41377-021-00614-6 ◽

2021 ◽

Vol 10 (1) ◽

Author(s):

Mengying Hu ◽

Ye Zhang ◽

Xi Jiang ◽

Tong Qiao ◽

Qiang Wang ◽

...

Keyword(s):

Surface States ◽

Nodal Line ◽

Electronic Systems ◽

Nodal Lines ◽

Spectrum Range ◽

The Past ◽

Topological Materials ◽

Classical Waves ◽

Topological Semimetals ◽

Polarized Surface

AbstractThe past decade has seen a proliferation of topological materials for both insulators and semimetals in electronic systems and classical waves. Topological semimetals exhibit topologically protected band degeneracies, such as nodal points and nodal lines. Dirac nodal line semimetals (DNLS), which own four-fold line degeneracy, have drawn particular attention. DNLSs have been studied in electronic systems but there is no photonic DNLS. Here in this work, we provide a new mechanism, which is unique for photonic systems to investigate a stringent photonic DNLS. When truncated, the photonic DNLS exhibits double-bowl states (DBS), which comprise two sets of perpendicularly polarized surface states. In sharp contrast to nondegenerate surface states in other photonic systems, here the two sets of surface states are almost degenerate over the whole-spectrum range. The DBS and the bulk Dirac nodal ring (DNR) dispersion along the relevant directions, are experimentally resolved.

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Dirac nodal surfaces and nodal lines in ZrSiS

Science Advances ◽

10.1126/sciadv.aau6459 ◽

2019 ◽

Vol 5 (5) ◽

pp. eaau6459 ◽

Cited By ~ 26

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.

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Robust topological nodal lines in halide carbides

Physical Chemistry Chemical Physics ◽

10.1039/c9cp04330f ◽

2019 ◽

Vol 21 (36) ◽

pp. 20262-20268 ◽

Cited By ~ 6

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.

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Crystallinity of tellurium capping and epitaxy of ferromagnetic topological insulator films on SrTiO3

Scientific Reports ◽

10.1038/srep11595 ◽

2015 ◽

Vol 5 (1) ◽

Cited By ~ 9

Author(s):

Jihwey Park ◽

Yeong-Ah Soh ◽

Gabriel Aeppli ◽

Xiao Feng ◽

Yunbo Ou ◽

...

Keyword(s):

Crystal Structure ◽

Electronic Structure ◽

Transport Properties ◽

Topological Insulator ◽

Topological Insulators ◽

Surface States ◽

Crystal Quality ◽

X Rays ◽

Capping Layer ◽

Subtle Effect

Abstract Thin films of topological insulators are often capped with an insulating layer since topological insulators are known to be fragile to degradation. However, capping can hinder the observation of novel transport properties of the surface states. To understand the influence of capping on the surface states, it is crucial to understand the crystal structure and the atomic arrangement at the interfaces. Here, we use x-ray diffraction to establish the crystal structure of magnetic topological insulator Cr-doped (Bi,Sb)2Te3 (CBST) films grown on SrTiO3 (1 1 1) substrates with and without a Te capping layer. We find that both the film and capping layer are single crystal and that the crystal quality of the film is independent of the presence of the capping layer, but that x-rays cause sublimation of the CBST film, which is prevented by the capping layer. Our findings show that the different transport properties of capped films cannot be attributed to a lower crystal quality but to a more subtle effect such as a different electronic structure at the interface with the capping layer. Our results on the crystal structure and atomic arrangements of the topological heterostructure will enable modelling the electronic structure and design of topological heterostructures.

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Topological Insulators: Electronic Structure, Material Systems and Applications

International Journal of High Speed Electronics and Systems ◽

10.1142/s0129156417400183 ◽

2017 ◽

Vol 26 (03) ◽

pp. 1740018

Author(s):

Parijat Sengupta

Keyword(s):

Quantum Wells ◽

Topological Insulator ◽

Topological Insulators ◽

Tight Binding ◽

Surface States ◽

Internal Electric Field ◽

Linear Dispersion ◽

Band Theory ◽

Magnetic Perturbations ◽

Polarized Surface

Topological insulators are a new class of materials characterized by fully spin-polarized surface states, a linear dispersion, imperviousness to external non-magnetic perturbations, and a helical character arising out of the perpendicular spin-momentum locking. This article answers in a pedagogical way the distinction between a topological and normal insulator, the role of topology in band theory of solids, and the origin of these surface states. Numerical techniques including diagonalization of the TI Hamiltonians are described to quantitatively evaluate the behaviour of topological insulator states. The Hamiltonians based on continuum and tight binding approaches are contrasted. The application of TIs as components of a fast switching environment or channel material for transistors is examined through I-V curves. The potential pitfall of such devices is presented along with techniques that could potentially circumvent the problem. Additionally, it is demonstrated that a strong internal electric field can also induce topological insulator behaviour with wurtzite nitride quantum wells as representative materials.

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Magnetism-induced topological transition in EuAs3

10.21203/rs.3.rs-100461/v1 ◽

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.

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A Chemical Theory of Topological Insulators

10.26434/chemrxiv.7637009 ◽

2019 ◽

Author(s):

Angel Martín Pendás ◽

Julia Contreras-García ◽

Fernanda Pinilla ◽

José Daniel Mella ◽

Carlos Cárdenas ◽

...

Keyword(s):

Topological Insulators ◽

Surface States ◽

Chemical Theory ◽

Protected Surface ◽

Symmetry Protected ◽

Chemical Description

This article presents a chemical description of a simple topological insulators model in order to translate concepts such as "symmetry protected", "surface states" to the chemistry vocabulary

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