High-harmonic generation in a quantum electron gas trapped in a   nonparabolic and anisotropic well
  An effective self-consistent model is derived and used to study the dynamics of an electron gas confined in a nonparabolic and anisotropic quantum well. This approach is based on the equations of quantum hydrodynamics, which incorporate quantum and nonlinear effects in an approximate fashion. The effective model consists of a set of six coupled differential equations (dynamical system) for the electric dipole and the size of the electron gas. Using this model we show that: (i) High harmonic generation is related to the appearance of chaos in the phase space, as attested by related Poincar\'e sections; (ii) Higher order harmonics can be excited efficiently and with relatively weak driving fields by making use of chirped electromagnetic waves. 
Jerome Hurst, Kevin Leveque-Simon, Paul-Antoine Hervieux, Giovanni   Manfredi, Fernando Haas
cond-mat.mes-hall cond-mat.str-el