Exciton magnetotransport in two-dimensional systems: Weak-localization effects

We consider the effect of a magnetic field $B$ on the transport of neutral composite particles, excitons, in weakly disordered 2D systems. In the case of classical transport, when the interference of different paths is neglected, the magnetic field suppresses exciton transport, and the static diffusion constant $D(B)$ monotonically drops with $B$. When quantum-mechanical corrections due to weak localization are taken into account, $D(B)$ becomes a nonmonotonic function of $B$. In weak magnetic fields, where the magnetic length is much larger than the exciton Bohr radius, $l_B >> a_B$, a positive magnetodiffusion effect is predicted, i.e., the exciton mobility should increase with $B$.