Intrawell and interwell magnetoexcitons in ${\mathrm{In}}_{\mathit{x}}$${\mathrm{Ga}}_{1\mathrm{-}\mathit{x}}$As/GaAs coupled double quantum wells

We theoretically study the ground and many of the excited optically active s states of spatially direct (intrawell) and indirect (interwell) quasi-two-dimensional excitons in ${\mathrm{In}}_{\mathit{x}}$ ${\mathrm{Ga}}_{1\mathrm{-}\mathit{x}}$As/GaAs coupled double quantum wells (DQW’s) in quantizing magnetic fields B≳2 T. The evolution of the eigenstates and oscillator strengths with the perpendicular magnetic B and electric E fields (when, in particular, the direct-indirect crossover and a number of anticrossings occur in the spectra) is studied. The results of the theory are in good agreement with the recently obtained experimental data [L. V. Butov, A. Zrenner, G. Abstreiter, A. V. Petinova, and K. Eberl, Phys. Rev. B 52, 12 153 (1995)]. The physical origin of the excitonic symmetric-antisymmetric splittings ${\mathrm{\Delta }}_{\mathit{X}}$ in DQW’s is discussed. It is shown that, in the wide-barrier regime, ${\mathrm{\Delta }}_{\mathit{X}}$ are determined by the two-particle tunneling through the barrier and suppressed by the excitonic effects. ©1996 The American Physical Society.