Dynamic approach to the ground state of a vortex system with random pinning

We, study the ground state of a two-dimensional vortex system with random p innings by cooling the vortex system to zero temperature. The peak of struc ture factor S(k) of vortices increases with vortex density B but decreases with pin density B-phi, indicating that the vortex lattice becomes better a nd better ordered with increasing B. When B > B-phi, the triangular vortex lattice is observed away from the pins. Repulsive vortex interactions destr oy the Mott insulator phase which is predicted to occur at B = B-phi. The c rossover line between the strong Bose glass and the weak Bose glass is near ly independent of B-phi for small B-phi.