About the cover
A representation of hysteresis in a quantized superfluid atomtronic circuit based on an image of a trapped ring-shaped BoseEinstein condensate (BEC). Hysteresis, a phenomenon by which the physical properties of a system depend strongly on the history of the applied perturbation, is widely exploited in electronic circuits including hard disk drives and flux-gate magnetometers and is essential to the function of radio-frequency SQUIDs (superconducting quantum interference devices). Hysteresis is also fundamental to superfluidity and has been predicted to occur in superfluid atomic-gases, such as BECs. Gretchen Campbell and colleagues now report the first direct detection of hysteresis between quantized circulation states in a circuit formed from a ring of superfluid BEC obstructed by a rotating weak link. The presence of hysteresis in this system is of importance in the emerging field of atomtronics, in which ultracold atoms have a role analogous to that of the electrons in electronics. Controlled hysteresis in atomtronic circuits may prove to be a crucial feature for the development of practical devices. Cover: Emily Edwards.