Acoustic topological devices based on emulating and multiplexing of pseudospin and valley indices

Abstract

We present a design paradigm for acoustic devices in which robust and controllable transport of wave signals can be realized. These devices are based on a simple acoustic platform, where different topological phases such as acoustic quantum spin Hall and quantum valley Hall insulators are emulated by engineering the spatial symmetries of the structure. Edge states along interfaces between different topological phases are shown to be promising information channels, where the multiplexing of pseudospin and/or valley degrees of freedom is unambiguously demonstrated in various devices including a multiport valve for acoustic power dividing and feeding. The information capacity in the input channel is substantially enhanced due to the creating of an extra dimension for the data carriers. The topological devices proposed here, when integrated with other state-of-the-art communication techniques, may suggest a significant step towards acoustic communication circuits with complex functionalities.

Topological sound in two dimensions

“…[113][114][115] The robustness of edge modes is sustained by the symmetries of the -broken lattice, hence they are protected only against defects that do not mix chiralities, allowing for topological beam splitters 113 (Figure 4E), as well as directional antennas 116,117 (Figure 4D) and acoustic delay lines 118 (Figure 4D) that can benefit from the high degree of tunability offered by phononic platforms. 119,120 Bilayer metamaterials offer valley topological phases with more DOFs, such as valley or layer polarization in the same device [121][122][123] (Figure 4F).…”

Imaginary spin-orbital coupling in parity-time symmetric systems with momentum-dependent gain and loss

“…And in condensed matter physics, the investigation of SOC has led to fruitful achievements (such as the spin-Hall effect [3], topological insulator [4], just name a few) with potential applications in spintronics [5] and quantum computations [6]. Currently, SOC researches are drastically expanding to the fields of cold atom physics [7][8][9][10][11][12][13][14][15][16][17][18][19][20][21][22], optics [23][24][25][26][27][28][29] and acoustics [30][31][32][33][34]. Cold atom systems have no natural SOC, whereas using the Raman coupling scheme [11] (and also some others, see the review article [12]) artificial SOC has been experimentally realized, furthermore supersolid stripe states [13][14][15][16][17][18][19][20] and momentum-space Josephson oscillations [21,22] can be generated.…”

“…In dual-core waveguides, SOC can be synthesized by dispersively coupling the light field in different cores [26][27][28], and stripe solitons can be produced [29]. In acoustical systems, SOC has also been successfully synthesized [30][31][32][33][34].…”

Topological radiation engineering in hyperbolic sonic semimetals

“…On a different but at least equally exciting frontier, we find topological insulators, which constitute a paradigm of media and structures to permit and tailor unusual wave guidance [7]. In both time reversal symmetric and broken scenarios or by utilizing structures of specific symmetries to enable certain quantum phases, robust guiding and control of sound waves have been brought forward that abide by the bulkedge correspondence [8][9][10][11][12]. Beyond this concept, phononic higher-order topological insulators and other so-called zero modes have seen the light of day in many groundbreaking experiments [13][14][15].…”