  We propose an efficient design route to generate unidirectional propagation
of the designer surface acoustic waves. The whole system consists of a
periodically corrugated rigid plate combining with a pair of asymmetric narrow
slits. The directionality of the structure-induced surface waves stems from the
destructive interference between the evanescent waves emitted from the double
slits. The theoretical prediction is validated well by simulations and
experiments. Promising applications can be anticipated, such as in designing
compact acoustic circuits.
