Giant isochoric compressibility of solidHe4: The bistability of superclimbing dislocations

Abstract

A significant accumulation of matter in solid Helium-4 observed during the superflow events, dubbed as the giant isochoric compressibility (or the syringe effect), is discussed within the model of dislocations with superfluid core. It is shown that solid Helium-4 in a contact with superfluid reservoir can develop a bistability with respect to the syringe fraction, with the threshold for the bias by chemical potential determined by a typical free length of dislocations with superfluid core. The main implications of this effect are: hysteresis and strongly non-linear dynamical behavior leading to growth, proliferation and possibly exiting from a crystal of superclimbing dislocations. Three major channels for such dynamics are identified: i) injection and inflation of the prismatic loops from the boundary; ii) Bardeed-Herring generation of the loops in the bulk; iii) helical instability of the screw dislocations. It is argued that the current experiments are likely to be well in this regime. Several testable predictions for the time and the bias dependencies of the dynamics are suggested