Periodic Orbit Theory of the Transition to Chaos in Quantum Wells
  An analytic theory is developed for the density of states oscillations in quantum wells in a magnetic field which is tilted with respect to the barrier planes. The main oscillations are found to come from the simplest one or two-bounce periodic orbits. We calculate their period and stability analytically and find an infinite sequence of destabilizations followed by restabilizations as the chaos parameter increases. This phenomenon explains the re-entrant frequency-doubling of the density of states peaks observed in recent magnetotunneling experiments. 
E.E.Narimanov and A.D.Stone (Yale University)