Second-harmonic generation in quantum wells: the role of many-body effects

We study theoretically the influence of the Coulomb interaction on the second-harmonic generation (SHG) connected with intersubband transitions in asymmetric quantum wells. Our approach is based on the time-dependent local density approximation. Numerical calculations are performed for asymmetric coupled double quantum well structure with small energy separation between ground and excited subbands. It was shown that the Coulomb interaction not only shifts the peak positions in SHG spectrum but also considerably modifies their height. The correct description of the above modification must take into account the nonlinear dependence of the exchange-correlation potential on the electron density.