Quantum states in a magnetic antidot

We study a system in which electrons in two dimensions are confined by a nonhomogeneous magnetic field. The system consists of a heterostructure with a superconducting disk on top of it. We show that in this system electrons can be confined into a dot region. This magnetic antidot has the interesting property that the filling of the dot is a discrete function of the magnetic field. For some of the bound states the circulating electron current inside and outside the antidot can be in opposite direction. Such states exhibit a diamagnetic to paramagnetic transition with increasing magnetic field. The absorption spectrum consists of many peaks, some of which violate Kohn's theorem, which is due to the coupling of the center-of-mass motion with the other degrees of freedom. [S0163-1829(99)03804-7].