Mechanism of shakeup processes in the photoluminescence of a two-dimensional electron gas at high magnetic fields

We observe shakeup processes in the photoluminescence spectra of a two-dimensional electron gas in a ${\mathrm{G}\mathrm{a}\mathrm{A}\mathrm{s}/\mathrm{A}\mathrm{l}}_x{\mathrm{Ga}}_{1-x}\mathrm{As}$ quantum well at high magnetic fields. We find that when the electrons occupy only the lowest Landau level these processes are strongly suppressed. We show that this behavior can be accounted for by first-principles calculations. We use the same considerations to explain the giant intensity of the shakeup line, which appears just below the main luminescence line.