Higher-Order Weyl Semimetals

Wang, Hai-Xiao; Lin, Zhi‐Kang; Jiang, Bin; Guo, Guang‐Yu; Jiang, Jian‐Hua

doi:10.1103/physrevlett.125.146401

Cited by 141 publications

(78 citation statements)

References 57 publications

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“…Interestingly for a HO Dirac semimetal, its gapped 2D slices may be classified into two HO topologically distinct insulators, for which the transition occurs exactly at the Dirac points 4,5 . Similar topological transitions also emerge in HO Weyl semimetals [12][13][14][15] . Such features lead to the presence of fascinating one-dimensional (1D) hinge modes connecting the projected Dirac or Weyl nodes, a robust manifestation of the HO bulk-hinge correspondence.…”

Section: Co-dimensionmentioning

confidence: 58%

“…Nontrivial HO topology has been predicted not only in gapped insulators [6][7][8][9][10][11] but also in gapless semimetals 4,5,[12][13][14][15] . These new HO members greatly enrich the already diverse spectrum of topological phases of matter.…”

Section: / 14mentioning

confidence: 99%

“…To date there have been extensive studies of various HO topological phases in condensed matter and materials physics [4][5][6][7][8][9][10][11][12][13][14][15][20][21][22][23][24][25][26] , ranging from solid-state materials to ultra-cold atoms, from photonics to acoustics, etc. In particular, the artificial crystals for classical waves have been demonstrated to be exceptional platforms for exploring those otherwise elusive topological phases, benefiting from their macroscopically more controllable structures and less demanding measurements 27,28 .…”

Section: / 14mentioning

confidence: 99%

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Higher-order Dirac sonic crystals

Qiu

Xiao

et al. 2020

Preprint

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Discovering new topological phases of matter is a major theme in fundamental physics and materials science1,2. Dirac semimetal features isolated fourfold linear band crossings, i.e., Dirac points, and provides an exceptional platform for exploring topological phase transitions under symmetry breaking3. Recent theoretical studies4,5 have revealed that a three-dimensional Dirac semimetal can harbor fascinating hinge states, a high-order (HO) topological manifestation not known before. However, realization of such a HO Dirac phase in experiment is yet to be achieved, not to mention the fascinating hinge states, although candidate solid-state materials have been suggested5. Here we propose a minimum model to construct a spinless HO Dirac semimetal protected by C_6v symmetry. By breaking different symmetries, this parent phase transitions into a variety of novel topological phases including HO topological insulator, HO Weyl semimetal, and HO nodal-ring semimetal. Furthermore, for the first time, we experimentally realize this unprecedented HO topological phase in a sonic crystal and unambiguously present the smoking-gun observation of the desired hinge states via momentun-space spectroscopy and real-space visualization. Our findings may offer new opportunities to manipulate classical waves such as sound and light.

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Section: Co-dimensionmentioning

confidence: 58%

Section: / 14mentioning

confidence: 99%

Section: / 14mentioning

confidence: 99%

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Higher-order Dirac sonic crystals

Qiu

Xiao

et al. 2020

Preprint

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“…This winding number is tied to the Chern number of the 2D projected band structure for fixed k z . The fact that the TLD-bound modes carry nonzero OAM, locked to the propagation direction, distinguishes them from previously studied topological defect modes 67 – 70 and hinge modes 56 , 57 , 61 that have zero OAM. Moreover, we have verified numerically that the TLD-bound modes’ localisation and OAM are robust to in-plane disorder, consistent with their topological origin (see Supplementary Note 3 ).…”

Section: Resultsmentioning

confidence: 84%

“…Recently, the discovery of higher-order topological materials 52 has led to the idea of higher-order Weyl and Weyl-like phases 53 – 61 , which can host “higher-order Fermi arcs” 56 – 58 , 61 . Like the TLD-bound modes discussed in this paper, higher-order Fermi arc modes are one-dimensional, but they arise from a completely different mechanism involving higher-order topological indices 56 , 57 , 61 . Moreover, they lie along external hinges, whereas the present TLD-bound modes are localised to the line of the TLD, embedded inside a 3D bulk.…”

Section: Resultsmentioning

confidence: 99%

Vortex states in an acoustic Weyl crystal with a topological lattice defect

Wang

Sun

et al. 2021

Nat Commun

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Crystalline materials can host topological lattice defects that are robust against local deformations, and such defects can interact in interesting ways with the topological features of the underlying band structure. We design and implement a three dimensional acoustic Weyl metamaterial hosting robust modes bound to a one-dimensional topological lattice defect. The modes are related to topological features of the bulk bands, and carry nonzero orbital angular momentum locked to the direction of propagation. They span a range of axial wavenumbers defined by the projections of two bulk Weyl points to a one-dimensional subspace, in a manner analogous to the formation of Fermi arc surface states. We use acoustic experiments to probe their dispersion relation, orbital angular momentum locked waveguiding, and ability to emit acoustic vortices into free space. These results point to new possibilities for creating and exploiting topological modes in three-dimensional structures through the interplay between band topology in momentum space and topological lattice defects in real space.

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Tunable and Reconfigurable Higher‐Order Topological Insulators in Photonic Crystals with Phase Change Materials

Zhang

et al. 2021

Annalen der Physik

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Higher-order topological insulators (HOTIs) have attracted great interest due to the unconventional bulk-boundary correspondence. However, the realization of HOTIs usually requires a geometrical transformation of the photonic crystals (PhCs), setting high demands on the manufacturing process. Here a scheme is reported of tunable and reconfigurable HOTIs with phase change materials (PCMs) by controlling the temperature. The temperature change can transform the amorphous states to crystalline states, leading to the reconfigurable edge states and corner states. It is proven that both Sb 2 S 3 and Sb 2 Se 3 can support the reconfigurable HOTIs at the phase change temperature 270 °C at different wavelengths. This work discovers a new platform for the practical implementation of high-order topological phase transition optical apparatus in the foreseeable future, such as nanocavities, waveguides, and metasurfaces.

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Higher-Order Weyl Semimetals

Cited by 141 publications

References 57 publications

Higher-order Dirac sonic crystals

Higher-order Dirac sonic crystals

Vortex states in an acoustic Weyl crystal with a topological lattice defect

Tunable and Reconfigurable Higher‐Order Topological Insulators in Photonic Crystals with Phase Change Materials

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