Long-lasting Exponential Spreading in Periodically Driven Quantum   Systems
  Using a dynamical model relevant to cold-atom experiments, we show that long-lasting exponential spreading of wave packets in momentum space is possible. Numerical results are explained via a pseudo-classical map, both qualitatively and quantitatively. Possible applications of our findings are also briefly discussed. 
Jiao Wang, Italo Guarneri, Giulio Casati, and Jiangbin Gong
nlin.CD quant-ph