Magnetic Response of Disordered Ballistic Quantum Dots

The weak field average magnetic susceptibility of square shaped mesoscopic conductors is studied within a semiclassical framework. Long semiclassical trajectories are strongly affected by static disorder and differ sharply from those of clean systems. They give rise to a large linear paramagnetic susceptibility which is disorder independent and in agreement with recent experiments. The crossover field to a nonlinear susceptibility is discussed.