Superradiance of nearly condensed excitons in InAs-GaSb coupled quantum wells

We suggest a system of ground state excitons in multiple InAs-GaSb coupled quantum wells as a new source of superradiance. Coupled InAs-GaSb quantum wells can be tuned to a very large wavelength that makes it possible to fabricate a sample with a large number of quantum wells radiating in phase, and in this way to increase the superradiant effect. Depending on the parameters of the system, this superradiance may be a direct analogy of the known Dicke case, or a realization of new type $N$-level superradiance. In the last case, the time dependence of the luminescence presents $N$ decaying peaks. This dependence may be considered as a manifestation of transition to the Bose condensate phase.

Figure 1

(Color online) Time dependence of the normalized radiation rate of equally excited 20 emitters. If initially the emitters are excited to the first level (1 exciton in each emitter), the radiation rate has 1 peak. Excitation to the second level (2 excitons in each emitter) gives 2 peaks, excitation to the third level (3 excitons) gives 3 peaks, and so on. The peaks are followed by exponential decay.

Figure 2

(Color online) Time dependence of the normalized radiation rate of emitters excited to the 10th level (10 excitons in each emitter). With an increase in the number of emitters, the peaks become more narrow and more pronounced.

Figure 3

(Color online) Dynamics of radiation and population of oscillator levels. Peaks of the radiation rate coincide with the equal population of the two neighboring levels.

Figure 4

(Color online) Smearing of the initial level population leads to the smearing of the radiation peaks.