Showing papers by "Manzhu Ke published in 2019"
TL;DR: In this article, an experimental realization of a giant uniform pseudomagnetic field in acoustics by introducing a simple uniaxial deformation to the acoustic graphene was reported.
Abstract: Many intriguing phenomena occur for electrons under strong magnetic fields1,2. Recently, it was shown that an appropriate strain texture in graphene could induce a synthetic gauge field3–6, in which electrons behave as they do in a real magnetic field7–11. This enabled the control of quantum transport by mechanical means and allowed the unreached high-field regime to be explored. Such synthetic gauge fields have been achieved in molecular12 and photonic13 lattices. Here we report an experimental realization of a giant uniform pseudomagnetic field in acoustics by introducing a simple uniaxial deformation to the acoustic graphene. The controllability of our macroscopic platform enables us to observe the acoustic Landau levels in frequency-resolved spectroscopy and their spatial localization in pressure-field distributions. We further visualize the quantum-Hall-like edge states (connected to the zeroth Landau level), which have been elusive owing to the difficulty in creating large-area uniform pseudomagnetic fields5,6. These results, consistent with our full-wave simulations, establish a complete framework for artificial structures under constant pseudomagnetic fields. Our findings may also offer opportunities to manipulate sound in conceptually novel ways. A graphene-like two-dimensional sonic crystal, under uniaxial deformation, experiences a giant uniform pseudomagnetic field. This leads to the quantization of the cyclotron orbits—a kind of acoustic Landau level—that is observed here.
80 citations
TL;DR: This Letter explores the intriguing Weyl physics by a simple one-dimensional sonic crystal, in which two extra structural parameters are combined to construct a synthetic three-dimensional space, and probed the novel reflection phase singularity that connects inherently with the topological robustness of Weyl points.
Abstract: Recently, intense efforts have been devoted to realizing classical analogues of various topological phases of matter. In this Letter, we explore the intriguing Weyl physics by a simple one-dimensional sonic crystal, in which two extra structural parameters are combined to construct a synthetic three-dimensional space. Based on our ultrasonic experiments, we have not only observed the synthetic Weyl points, but also probed the novel reflection phase singularity that connects inherently with the topological robustness of Weyl points. The presence of topologically nontrivial interface modes has been demonstrated further. As the first realization of topological acoustics in synthetic space, our study exhibits great potential of probing high-dimensional topological phenomena by such easily fabricated and detected low-dimension acoustic systems.
52 citations
TL;DR: In this paper, the authors report an experimental study on the valley-projected edge states for underwater sound propagation, which propagates along the interface separating two topologically distinct acoustic valley Hall insulators.
Abstract: Here, we report an experimental study on the valley-projected edge states for underwater sound, which propagates along the interface separating two topologically distinct acoustic valley Hall insulators The topological edge states are directly observed in our ultrasound scanning experiments, together with a solid evidence for the valley-selective excitation Furthermore, we demonstrate an intriguing sound splitter built by topologically different acoustic valley Hall insulators All experimental data agree well with our numerical results Prospective applications can be anticipated, such as for underwater sound signal processing and ocean noise control
35 citations
TL;DR: In this article, a three-dimensional acoustic metacrystal that hosts topological nodal lines pinning to the edges of a Brillouin zone has been constructed, where the nodal line is geometrically straight and fully stabilized by the crystal symmetry.
Abstract: Recently, topological semimetals featured with symmetry-protected nodal line degeneracies in three-dimensional momentum space have attracted great attention. In this work, we have constructed a three-dimensional acoustic metacrystal that hosts topological nodal lines pinning to the edges of a Brillouin zone. Markedly different from the nodal rings or chains observed previously, here the nodal lines are geometrically straight and fully stabilized by the crystal symmetry, which are highly unique and favored for detection. In addition to the symmetry-enforced nodal lines identified by transmission measurements, exotic waterslidelike surface states have been unveiled through scanning surface fields. Excellent agreements are found between our experiments and simulations. Our study may provoke new possibilities for controlling sound, such as realizing unusual sound radiation and scattering.
19 citations
TL;DR: In this paper, a sound splitter using the orbital angular momentum (OAM) of acoustic vortices is proposed and experimentally demonstrated using a helical waveguide with a periodic array of shunted tubes.
Abstract: A sound splitter using the orbital angular momentum (OAM) of acoustic vortices is proposed and experimentally demonstrated. We show that a helical waveguide with a periodic array of shunted tubes can be used to achieve different transmission spectra for the acoustic vortices with opposite OAM topological charges due to their different Bragg scattering type bandgaps. By symmetry, the transmission spectra will reverse if the handedness of the helical waveguides is changed. Therefore, two such composite waveguides with opposite handedness can be combined to separate the OAM-dependent flow of sound. Our study of the acoustic vortex splitter may provide a route for demultiplexing in acoustic OAM-based communication.
12 citations
TL;DR: In this article, a meta-rod structure was proposed to achieve the $s\phantom{\rule{0}{0ex}}o \phantom{0}ex}}u\phanto{0},0ex}n\phono{0, 0, 0ex} n\pho{0, 0, 0ex}}n \pho[0]ex]n\Pho[ 0,0,0ex]g$ effect in the subwavelength regime of a metamaterial.
Abstract: Strong enhancement of sound scattering is important for some applications of acoustic metamaterials, such as sensing and acoustic antennae. Here the authors create a meta-rod structure to achieve the $s\phantom{\rule{0}{0ex}}o\phantom{\rule{0}{0ex}}u\phantom{\rule{0}{0ex}}n\phantom{\rule{0}{0ex}}d$ $s\phantom{\rule{0}{0ex}}u\phantom{\rule{0}{0ex}}p\phantom{\rule{0}{0ex}}e\phantom{\rule{0}{0ex}}r\phantom{\rule{0}{0ex}}s\phantom{\rule{0}{0ex}}c\phantom{\rule{0}{0ex}}a\phantom{\rule{0}{0ex}}t\phantom{\rule{0}{0ex}}t\phantom{\rule{0}{0ex}}e\phantom{\rule{0}{0ex}}r\phantom{\rule{0}{0ex}}i\phantom{\rule{0}{0ex}}n\phantom{\rule{0}{0ex}}g$ effect. The near-degeneracy of resonances in multiple channels of the meta-rod can break the so-called single-channel limit of subwavelength structures, and thus achieve extremely strong sound scattering, even in the deeply subwavelength regime. The mechanism behind superscattering of sound turns out to be more robust than that for light, so there are not stringent fabrication requirements for the proposed structure, which is important for practical applications.
11 citations
TL;DR: In this paper, the authors describe the fabrication of an annular anisotropic metamaterial with an azimuthal effective density approaching zero and demonstrate its robust omnidirectional radiation performance.
Abstract: Acoustic metamaterials are artificial structures with unique properties that offer great flexibility for manipulating acoustic waves. In this manuscript, we describe the fabrication of an annular anisotropic metamaterial with an azimuthal effective density approaching zero and demonstrate its robust omnidirectional radiation performance. Locating two sources at a distance from one another or placing a cross-shape obstacle between them inside the cavity of the metamaterial produces acoustic omnidirectional radiation over a wide frequency range. This is quite different from the behavior in the cavity mode. This anisotropic zero-density metamaterial can be considered as a source shifter, which may have applications in acoustic manipulation, acoustic communication, cloaking, and sonar systems.
5 citations
TL;DR: This work observes quadratic Weyl points and identifies double-helicoid surface arcs in sound waves traveling in a three-dimensional chiral metacrystal of sound waves to provide conclusive evidence for the double topological charges of such unconventional topological nodes.
Abstract: 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 science1-9. Here we report the first experimental observation of the long-desired quadratic Weyl points10 by using a three-dimensional chiral metacrystal of sound waves. Markedly different from the newly observed unconventional quasiparticles5-9, 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 one10. 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.
3 citations