Effects of disorder on vortex dynamics in Bose-Einstein Condensates

Collective excitations are low-energy excitations which are seen in the interacting system, where one can observe the collective behavior of particles. My interest is to study such excitations like vortices in Bose-Einstien condensates (BECs). The study of collective excitations opened a new platform to compare the system with other systems like superconductors and superfluid helium. A rotating BEC mimics a type-II superconductor in applied magnetic field and its response to rotation reveals superfluid behavior. A vortex in BEC is a density zero region with localized phase singularity, while in a super conductor it is the region of flux penetration. Recently, we have investigated the vortex dynamics, vortex pinning and vortex lattice melting in BEC system. It is shown that similar to the case type-II superconductor a vortex follows spiral path before it gets pinned with the impurity. In BECs, impurities are created artificially because the medium is pure. When an optical lattice is applied, the whole vortex lattice is transformed in to the shape of optical lattice as a result of pinning. On the other hand when impurities are placed in a random way, the vortex lattice became a disordered one as a result of pinning of vortices in randomly distributed pinning sites. Such studies have much impacts in superconductor system, where studies are limited due to the presence of natural impurities. BEC provides a system where it is possible to display in a controlled way the interplay between interaction and disorder on the vortex dynamics.