We investigate the effect of slow light propagating in a degenerate atomic
Fermi gas. In particular we use slow light with an orbital angular momentum. We
present a microscopic theory for the interplay between light and matter and
show how the slow light can provide an effective magnetic field acting on the
electrically neutral fermions, a direct analogy of the free electron gas in an
uniform magnetic field. As an example we illustrate how the corresponding de
Haas-van Alphen effect can be seen in a neutral gas of fermions.Comment: Slightly updated. Phys. Rev. Lett. 93, 033602 (2004