Superfluid 3He in rotation
Experiments on vortices in rotating superfluid 3He have revealed phenomena which have not been observed in any other quantum liquid and have implications in fields beyond low-temperature physics. In 3He-A, vorticity may be supported by a continuous winding of the order parameter which gives rise to the observed continuous coreless vortices with two flow quanta. Exotic vortices with half-integer circulation quanta may also exist in this phase. In 3He-B, an abrupt change in the vortex-core structure has been explained theoretically as a topological phase transition involving half-quantum vortices. NMR experiments on rotating 3He-B have revealed that the cores of vortices observed possess spontaneously broken parity, manifested by their ferromagnetic superfluid cores.
Superfluid Helium 3 Topological Defects as a Consequence of Broken Symmetry
Superfluid phases in helium 3 were firstly discovered in 1972. They arise from the pairing of two fermionic helium 3 atoms to a composite boson, although there is a strong, short range repulsion between the atoms. These eects can be described using the Fermi liquid theory developed by Landau. But I will choose a dierent approach to the problem. Superfluidity is a macroscopic quantum phenomenom exhibiting spontaneous symmetry breaking. This characteristic can be understood by introducing an order parameter. Analyzing the structure of the order parameter you can explain the appearance of dierent superfluid phases. Furthermore, due to its complexity, superfluid
NMR Experiments on Rotating Superfluid 3He-A : Evidence for Vorticity
Experiments on rotating superfluid /sup 3/He-A in an open cylindrical geometry show a change in the NMR line shape as a result of rotation: The amplitude of the peak decreases in proportion to f(T)g(..cap omega..), where ..cap omega.. is the angular velocity of rotation; at the same time the line broadens. Near T/sub c/, f(T) is a linear function of 1-T/T/sub c/. At small velocities g(..cap omega..)proportional..cap omega... These observations are consistent with the existence of vortices in rotating /sup 3/He-A.