Self-consistent effects and breather mode in semiconductor quantum wells*

A novel breather mode in the self-consistent electron dynamics in semiconductor quantum wells is identified and characterized. The breather solution corresponds to coherent oscillations of the size of the electron gas around a self-consistent equilibrium. A non-perturbative time-dependent variational formalism is used to describe the relevant properties of the breather mode, both in the linear and nonlinear regimes, in the context of a quantum hydrodynamic model. The time-dependent Wigner-Poisson or Hartree equations are shown to be in excellent agreement with our analytical results. For asymmetric quantum wells, a signature of the breather mode is observed in the dipole response, which can be detected by standard optical means. The present approach should equally apply to metal nanoparticles and carbon-based systems such as fullerenes.