Generation and Demolishment Mechanisms of Vapor Bubble Around Hot Tungsten Filament in Superfluid Helium-4

The electric transport I – V characteristics of a tungsten filament immersed in superfluid helium are experimentally studied. The forward sweep I – V characteristics show an abrupt jump from the linear ohmic regime ( C  state) to the high-resistance non-ohmic regime ( H  state). In the H  state, the filament is covered with a He gas bubble. In the C  state, there is no gas bubble, that is, liquid He directly touches the filament surface. The transitions between these two states exhibit a well-developed hysteresis and bistability. The transition from the H state to the C  state occurs at the equilibrium gas–liquid phase transition point, as reported by Date et al. (J Phys Soc Jpn 35(4):1190, 1973), whereas the C -to- H -state transition occurs in the superheat region.