Observation of Double Weyl Phonons in Parity-Breaking FeSi

Miao, H.; Zhang, T. T.; Wang, L.; Meyers, D.; Said, Ayman; Wang, Y. L.; Shi, Youguo; Weng, Hongming; Fang, Zhujun; Dean, M. P. M.

doi:10.1103/physrevlett.121.035302

Cited by 177 publications

(111 citation statements)

References 30 publications

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“…QWPs and the consequent double-helicoid surface arcs emanating from and spiraling around the surface projection of a QWP. Both the local bulk dispersions near the QWPs and the global surface connectivity of the double-helicoid arcs to the QWPs and CWPs are unprecedented, in sharp contrast to all the other gapless topological matter realized to date [5][6][7][8][9][14][15][16][17]25,26,28 . In particular, our acoustic metacrystal is structurally simple and hosts three bands with connected QWPs and CWPs over a broad frequency range, providing an ideal platform for exploring the intriguing Weyl physics.…”

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confidence: 95%

“…Weyl points and charge-2 Dirac points have been experimentally realized [5][6][7][8][9] in solid-state materials soon after the theoretical predictions [1][2][3][4] . Unlike the conventional Weyl points (CWPs), the spin-1…”

mentioning

confidence: 97%

“…Most recently, novel quasiparticles beyond the conventional Dirac and Weyl ones, without any high-energy counterparts, have attracted tremendous attention [1][2][3][4][5][6][7][8][9] . Such unconventional quasiparticles, protected by crystalline symmetries in structurally chiral crystals, correspond to multifold (i.e., more than twofold) band crossings and carry higher topological charges.…”

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confidence: 99%

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Observation of quadratic Weyl points and double-helicoid arcs

Qiu

Cai

et al. 2020

Nat Commun

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Very recently, novel quasiparticles beyond those mimicking the elementary high-energy particles such as Dirac and Weyl fermions have attracted great interest in condensed matter physics and materials science 1-9 . Here we report the first experimental observation of the long-desired quadratic Weyl points 10 by using a three-dimensional chiral metacrystal of sound waves. Markedly different from the newly observed unconventional quasiparticles 5-9 , such as the spin-1 Weyl points and the charge-2 Dirac points that are featured respectively with threefold and fourfold band crossings, the charge-2 Weyl points identified here are simply twofold degenerate, and the dispersions around them are quadratic in two directions and linear in the third one 10 . Besides the essential nonlinear bulk dispersions, we further unveil the exotic double-helicoid surface arcs that emanate from a projected quadratic Weyl point and terminate at two projected conventional Weyl points through Fourier transformation of the scanned surface fields. This unique global surface connectivity provides conclusive evidence for the double topological charges of such unconventional topological nodes.

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confidence: 95%

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confidence: 97%

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confidence: 99%

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Observation of quadratic Weyl points and double-helicoid arcs

Qiu

Cai

et al. 2020

Nat Commun

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“…Recently, IXS has been used to study new emerging novel materials such as thermoelectric and topological materials. studies have led to better understanding of the role of lattice dynamics in superionic crystals (Niedziela et al, 2019), the observation of intrinsic localized modes (Manley et al, 2019) and double-Weyl phonons (Miao et al, 2018).…”

Section: Introductionmentioning

confidence: 99%

High-energy-resolution inelastic X-ray scattering spectrometer at beamline 30-ID of the Advanced Photon Source

Said¹,

Sinn²,

Toellner³

et al. 2020

J Synchrotron Rad

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Inelastic X-ray scattering is a powerful and versatile technique for studying lattice dynamics in materials of scientific and technological importance. In this article, the design and capabilities of the momentum-resolved high-energy-resolution inelastic X-ray spectrometer (HERIX) at beamline 30-ID of the Advanced Photon Source are reported. The instrument operates at 23.724 keV and has an energy resolution of 1.3–1.7 meV. It can accommodate momentum transfers of up to 72 nm−1, at a typical X-ray flux of 4.5 × 109 photons s−1 meV−1 at the sample. A suite of in situ sample environments are provided, including high pressure, static magnetic fields and uniaxial strains, all at high or cryogenic temperatures.

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“…The latest works have also focused on the influence of boundary conditions as well as the novel applications in negative refraction [28] and collimation effect [29]. The Weyl phonons in acoustic wave systems are different from those in condensed matter systems [32,33]. The acoustic wave systems do not contain transverse branches, but do contain the longitude branches in the band structure.…”

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confidence: 99%

Experimental Realization of Type-II Weyl Points and Fermi Arcs in Phononic Crystal

et al. 2019

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Weyl points (WPs), as the doubly degenerate points in three-dimensional momentum band structures, carry quantized topological charges and give rise to a variety of extraordinary properties, such as robust surface wave and chiral anomaly. Type-II Weyl semimetals, which have conical dispersions in Fermi surfaces and a strongly tilted dispersion with respect to type I, have recently been proposed in condensedmatter systems and photonics. Although the type-II WPs have been theoretically predicted in acoustics, the experimental realization in phononic crystals has not been reported so far. Here, we experimentally realize a type-II Weyl phononic crystal. We demonstrate the topological transitions observed at the WP frequencies and the topological surface acoustic waves between the Weyl frequencies. The experiment results are in good accordance with our theoretical analyses. Due to the violation of the Lorentz symmetry, the type-II WPs only exist in low energy systems. As the analog counterpart in classical waves, the phononic crystal brings a platform for the research of type-II WPs in macroscopic systems.

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Observation of Double Weyl Phonons in Parity-Breaking FeSi

Cited by 177 publications

References 30 publications

Observation of quadratic Weyl points and double-helicoid arcs

Observation of quadratic Weyl points and double-helicoid arcs

High-energy-resolution inelastic X-ray scattering spectrometer at beamline 30-ID of the Advanced Photon Source

Experimental Realization of Type-II Weyl Points and Fermi Arcs in Phononic Crystal

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