QUANTUM PARTICLES IN PERIODIC MAGNETIC-FIELDS

We consider a charged quantum particle moving in two dimensions subjec t to a magnetic field perpendicular to the plane. The field has a peri odic spatial variation. If the net-flux through a unit cell is a ratio nal number times the flux quantum, a gauge can be chosen so that Bloch 's theorem holds. This e.g. means that the eigenstates are extended Bl och waves. One example of this is the familiar Landau levels, which he re is to be interpreted as bands. The general result is analogous to t he case made famous by Hofstadter, where the periodicity was in a conv entional potential and not in the magnetic field. We predict oscillati ons in the conductance similar to the recently discovered Weiss-oscill ations.