Pseudo spin transport in cold atom systems

Abstract

This report presents theoretical predictions of the behavior of spin polarized systems in motion. More specifically, it looks at systems which have been configured to contain only two specific spin states. When a magnetic field is applied the two different "species" undergo different accelerations, resulting in interspecies collisions that, due to momentum transfer between the spin states, tend the system to an equilibrium with equal drift velocities of each spin species. This drag phenomenon is the primary focus of this report. By using the Boltzmann equation we predict quantum effects within a range of drift velocities around zero. The boson system portrays Bose-enhancement (significantly higher momentum transfer), while the fermion system manifests Pauli blocking (significantly lower momentum transfer). More remarkably, the boson-fermion system shows its own unique kind of blocking effect. Attention is also given to diffusion. The consideration of the system close to equilibrium allows for a derivation of the diffusion constant by using the Einstein relation.