Topological Acoustics

Abstract

The manipulation of acoustic wave propagation in fluids has numerous applications, including some in everyday life. Acoustic technologies frequently develop in tandem with optics, using shared concepts such as waveguiding and metamedia. It is thus noteworthy that an entirely novel class of electromagnetic waves, known as "topological edge states," has recently been demonstrated. These are inspired by the electronic edge states occurring in topological insulators, and possess a striking and technologically promising property: the ability to travel in a single direction along a surface without backscattering, regardless of the existence of defects or disorder. Here, we develop an analogous theory of topological fluid acoustics, and propose a scheme for realizing topological edge states in an acoustic structure containing circulating fluids. The phenomenon of disorder-free one-way sound propagation, which does not occur in ordinary acoustic devices, may have novel applications for acoustic isolators, modulators, and transducers.

Tight-binding methods for general longitudinally driven photonic lattices: Edge states and solitons

“…Fundamental research in systems where timereversal symmetry is broken have been found to support unidirectional edge modes that remain intact over long distance and against defects; these systems include magneto-optics [1,2], photonics [3][4][5] and acoustics [6]. While these systems have very different underlying physics they all share some common properties; they have a boundary that separates two distinct regions.…”

Conical wave propagation and diffraction in two-dimensional hexagonally packed granular lattices

“…From an experimental perspective, these systems appear to be well within reach since either in the realm of beads [51,52], or even in the more recent setup of magnets [56], it should be possible to construct a system tantamount to the one considered here, bearing in mind the considerable insights that their optical (even linear) analogues have offered; for a recent example, see [57]. Finally, this realization, in turn, would pave the way for additional intriguing features such as potential acoustic realizations [58] of topological edge states cf. [59][60][61][62], among others.…”

Experimental verification of acoustic pseudospin multipoles in a symmetry-broken snowflakelike topological insulator

“…Topological states have also been extended to condensed-matter physics based on the quantum Hall effect (QHE) [1,2], the quantum spin Hall effect (QSHE) [3,4], and topological insulators (TIs) [5,6]. Over the past ten years, investigation into new topologically protected edge states has started to grow in other subfields of physics, such as photonics [7][8][9][10][11][12][13][14][15][16], phononics [17][18][19][20][21][22][23][24][25][26][27][28][29][30][31][32], and mechanics [33][34][35][36]. The intrinsic difference between electrons and acoustic waves represents a great challenge in creating the spinlike degree of freedom for sound only possessing longitudinal polarization.…”