Nonlinear regime of oscillatory relaxation of photoexcited electrons in tunnel-coupled quantum wells

We investigate the nonlinear coherent dynamics of the electrons in an asymmetrical double-quantum-well system photoexcited by an ultrashort laser pulse, taking into account phase breaking due to elastic scattering. The nonlinearity takes place when the density of the electrons is high enough to modify the level-splitting energy of the tunnel-coupled states due to the space-charge effect. It is found that the combined effect of nonlinearity and dephasing leads to transitions (accompanied with jumps of the amplitude and phase of the oscillations) between different oscillatory regimes of the electron system during its temporal evolution. The relaxation of the photoexcited electrons in this case can proceed much faster than in the linear regime.