Broadband high-efficiency controllable asymmetric propagation by pentamode acoustic metasurface

We utilise the pentamode metasurface to realise broadband high-efficiency and controllable asymmetric transmission. The designed metasurface can manipulate the acoustic waves, as expected from the generalised Snell's law, and exhibits unique characteristics such as extraordinary broadband acoustic control, apparent negative refraction, and conversion from the propagating wave to surface mode. The asymmetric transmission features of positive refraction for the forward incidence (FI) and negative refraction for the reverse incidence (RI) can be realised within the range of 2600 Hz to 5600 Hz by controlling the incident angle from 0 degrees to 35 degrees with the transmission efficiency higher than 85.4% for the Fl and RI. In addition, by further adjusting the angle of incidence in the range of 25 degrees to 90 degrees, asymmetric transmission characteristics can be expressed as surface wave transmission for the Fl and transmitted wave transmission for the RI within the same frequency ranges. (C) 2020 Elsevier B.V. All rights reserved.