  With exciton lifetime much extended in semiconductor quantum-well structures,
their transport and Bose-Einstein condensation become a focus of research in
recent years. We reveal a momentum-space gauge field in the exciton
center-of-mass dynamics due to Berry phase effects. We predict spin-dependent
topological transport of the excitons analogous to the anomalous Hall and
Nernst effects for electrons. We also predict spin-dependent circulation of a
trapped exciton gas and instability in an exciton condensate in favor of vortex
formation.
