Soliton Diffusion as a Signature of Hawking Radiation in Bose-Einstein Condensates

We propose a scheme to detect analog Hawking radiation (HR) in an atomic Bose-Einstein condensate (BEC) through measuring the diffusion of a dark soliton. The HR is generated by changing the transverse trapping potential of the BEC to obtain a background flow, which is subsonic in downstream and supersonic in upstream, satisfying the condition of black hole horizon. When the system is in thermal equilibrium at Hawking temperature, a dark soliton is created in the upstream. Due to the influence of the HR, the motion of the dark soliton is similar to a Brownian particle and hence exhibits an apparent diffusion, which can be measured and be taken as a signal of the HR. Since the dark soliton is much heavier than Hawking quanta, its diffusion is much easier detectable than the Hawking quanta themselves.