Hysteresis at First-Order Wetting Transitions of 4He on Weak-Binding Substrates

4 He shows a first-order wetting transition on the weak-binding substrates Cs and Rb, as predicted theoretically and observed in experiment by several research groups. In these systems, the lifetime of metastable wetting states appears to be unusually long. The origin of this effect continues to be subject of a debate focussing on the relevance of thermal vs. substrate-disorder induced barriers between metastable states. It is shown here that wetting hysteresis strongly depends on the chosen initial state and its boundary conditions: depending on them, different hysteretic effects are probed. Quantitative estimates of the lifetime of two representative metastable states allow to assess the relevance of the two physically different hysteresis mechanisms for experiment.