Studies of coupled spin systems: In the context of supersolid behaviour in solid helium

Abstract

In recent years, there have been a lot of investigations, both experimental and theoretical of the possibility of simultaneous occurrence of crystalline order and super fluidity in solid helium. While there is still a lot of controversy about the microscopic mechanism of superfluidity in solid helium, there is increasing evidence that suggests that the superfluid component in this system resides primarily on structural defects such as dislocations and grain boundaries. In a three dimensional system, dislocations form a network of lines (one-dimensional objects) and grain boundaries form a network of two-dimensional planar objects. To study super fluidity on such networks, one first needs to construct realistic versions of the network. In the coupled spin models that we study in this context, one of the spin systems is used to generate the network of defects. We then study the equilibrium and dynamic properties of the coupled spin systems using numerical and analytical techniques.