A semiclassical theory is developed for the appearance of an excitation gap in a ballistic chaotic cavity connected by a point contact to a superconductor. Diffraction at the point contact is a singular perturbation in the limit , which opens up a gap in the excitation spectrum. The time scale (with the Lyapunov exponent) is the Ehrenfest time, the characteristic time scale of quantum chaos.
- Received 12 February 2002
- Published 14 November 2002
© 2002 The American Physical Society