MAGNETIZATION OF DISORDERED BALLISTIC QUANTUM BILLARDS

We study the magnetic response of mesoscopic quantum dots in the balli stic regime where the mean free path l(e) is larger that the size L of the sample, yet smaller than L(k(F)L)(d-1). In this regime, disorder plays an important role. Employing a semiclassical picture we calculat e the contribution of long tranjectories which are strongly affected b y static disorder and which differ sharply from those of clean systems . In the case of a magnetic field, they give rise to a large linear pa ramagnetic susceptibility (which is disorder independent), whose magni tude is in agreement with recent experimental results. In the case of a Aharonov-Bohm flux, the susceptibility is disorder dependent and is proportional to the mean free path as in the diffusive regime. We also discuss the corresponding non-linear susceptibilities.