Magnetic susceptibility of ballistic microstructures

The orbital magnetic susceptibility of ballistic microstructures is considered within the independent-electron model. Using semiclassical theory, specifically Gutzwiller’s trace formula, the finite-size corrections to the Landau susceptibility are expressed in terms of the classical periodic orbits. It is found that these finite-size corrections can be much larger than the bulk susceptibility in the quantum-coherent regime. It is demonstrated that the orbital susceptibility is a sensitive probe of quantum chaos, having a larger amplitude in integrable than in completely chaotic ballistic microstructures. The approach is applied to the square billiard. While the predictions for the amplitude and the magnetic-field dependence are consistent with recent experimental results by Lévy et al., the theory predicts a faster decrease with temperature than observed experimentally.