AHARONOV-BOHM BALLISTIC BILLIARDS

The measured orbital susceptibility of an array of 10(5) isolated Ga-As squares of area L2 = 4.5 x 4.5 mum2 has a paramagnetic contribution almost-equal-to k(F)L = 100 times larger than the Landau susceptibility. With increasing magnetic field, this paramagnetic susceptibility decreases on a field scale of order H-0 almost-equal-to phi0/L2, where phi0 = h/e is the flux quantum. As the temperature is raised, this orbital paramagnetism decreases on the scale of 0.5 K almost-equal-to E(c)/2 where E(c) = hupsilon(F)/L is the correlation energy. These experimental findings can be checked using Coulomb blockade spectroscopy. To this end, the thermodynamic relations between chemical potential and orbital currents are derived.