Spin angular momentum enables fundamental insights for topological matters, and practical implications for information devices. Exploiting the spin of carriers and waves is critical to achieving more controllable degrees of freedom and robust transport processes. Yet, due to the curl-free nature of longitudinal waves distinct from transverse electromagnetic waves, spin angular momenta of acoustic waves in solids and fluids have never been unveiled only until recently. Here, we demonstrate a metasurface waveguide for sound carrying non-zero acoustic spin with tight spin-momentum coupling, which can assist the suppression of backscattering when scatters fail to flip the acoustic spin. This is achieved by imposing a soft boundary of the π reflection phase, realized by comb-like metasurfaces. With the special-boundary-defined spin texture, the acoustic spin transports are experimentally manifested, such as the suppression of acoustic corner-scattering, the spin-selected acoustic router with spin-Hall-like effect, and the phase modulator with rotated acoustic spin.

自旋角动量可以为拓扑问题提供基本见解，并为信息设备提供实际意义。利用载流子和波的自旋对于实现更可控的自由度和稳健的传输过程至关重要。然而，由于纵波与横向电磁波不同的无卷曲性质，固体和流体中声波的自旋角动量直到最近才被发现。在这里，我们展示了一种用于携带具有紧密自旋动量耦合的非零声自旋的声音的超表面波导，当散射无法翻转声自旋时，它可以帮助抑制反向散射。这是通过施加π的软边界来实现的反射阶段，由梳状超表面实现。通过特殊边界定义的自旋纹理，声学自旋传输在实验上得到了证明，例如声学角散射的抑制、具有自旋霍尔效应的自旋选择声学路由器以及具有旋转声学自旋的相位调制器.