A Rayleigh-type wave at the plane interface of two homogeneous fluid half-spaces

It is shown that at the plane interface of two homogeneous fluid semi-infinite media, of which one is an ordinary fluid and the other a double negative-i.e., a fluid with negative density and negative compressibility-there can exist a Rayleigh-type wave propagating without attenuation, whose amplitude exponentially decreases with distance on both sides of the interface. In the parameter space of the media, the range of its existence is determined and the main properties are studied. A unique feature of this wave is the arbitrarily small propagation velocity, which does not depend on frequency, and the energy concentration in an arbitrarily thin layer close to the interface.