In its superfluid state, He-4 spreads out to form a thin film due to atomic interactions with the substrate (such as the walls of a container) far exceeding the scale of helium’s inter-atomic interactions. In our latest experiment these films form the basis of a simulated (2+1)-dimensional spacetime, with nanometric surface waves, referred to as third sound, creating the analogue of scalar quantum field excitations in a closed model universe.
We have developed a series of interferometric probes to allow us to observe third sound in thin films which act as passive observers of the spectrum of effective field excitations, opening new windows into the workings of quantum field theory.
