Impact of trans-Planckian excitations on black-hole radiation in dipolar condensates

We consider a quasi-one-dimensional dipolar condensate in a steplike analog black hole setup. It is shown that the existence of roton excitations leaves significant imprints onto the Hawking radiation spectrum. The emitted radiation depends on the depth of the roton minimum, and is in general more intense. In addition, we find a novel spontaneous particle creation mechanism with no counterpart in nondipolar condensates. Our results establish that dipolar condensates offer a richer and more versatile environment for the simulation of particle production from the quantum vacuum in the presence of horizon interfaces than contact-interaction condensates.