Screening of exciton states by quasi-two-dimensional electron gas in quantum wells

Changes in the binding energy and oscillator strength of an exciton state due to screening by a quasi-two-dimensional electron gas were calculated self-consistently in a nonlinear approximation. It was shown that the collapse of the bound state proceeds at very small concentrations $N_s \simeq 5 \times 10^9$ cm$^{-2}$, which is a consequence of taking into account the nonlinearity of the system response to the Coulomb perturbation.