CHAOTIC-TO-REGULAR TRANSITION IN A SEMICLASSICAL ELECTRON-GAS

We study the magnetic susceptibility chi of a two-dimensional noninter acting electron gas confined by a smooth chaotic potential. The comput ation of chi for a wide range of magnetic held values B reveals that t he chaotic (B = 0) to regular (B --> (infinity)) transition is dominat ed by bifurcations of short periodic orbits that become stable as B in creases. The families of stable orbits and tori contained in the assoc iated stability islands do not play any special role in this regime. L arge contributions, however, are observed near the bifurcation points, increasing the average susceptibility to values beyond those expected for regular systems.