Capacitive studies of hysteretic capillary condensation of superfluid ${}^4\mathrm{He}$ in Nuclepore have shown that the initial draining of the pores occurs over a small range of the chemical potential with avalanches present as groups of pores drain. In the work reported here, the avalanches in this system are shown to be nonlocal events which involve pores distributed at low density across the entire sample. The nonlocal avalanche behavior is shown to be enabled by the presence of a superfluid film connection among the pores.

• Received 31 May 1996

DOI:https://doi.org/10.1103/PhysRevLett.77.4222