QUANTUM CHAOS IN MAGNETIC BAND STRUCTURES

Magnetic band structures of an antidot superlattice in a perpendicular magnetic field are analysed with respect to signatures of quantum cha os. For an integer number of magnetic flux quanta threading a unit cel l, they show up in the distribution of nearest-neighbour level spacing s and the spectral rigidity. As the unique property of this infinite s ystem, we find in a single magnetic band structure coexistence of spec tra belonging to different universality classes depending on the magne tic wave vector. For a rational number of flux quanta the universal fe atures of quantum chaos disappear with increasing flux denominator and level clustering occurs in the spectrum although classical motion is widely chaotic.