Charged excitons in the fractional quantum Hall regime - art. no. 216402

We study the photoluminescence spectrum of a low-density (v < 1) two-dimens ional electron gas at high magnetic fields and low temperatures. We find th at the spectrum in the fractional quantum Hall regime can be understood in terms of singlet and triplet charged excitons. We show that these spectral Lines are sensitive probes for the electron compressibility. We identify th e dark triplet charged exciton and show that it is visible at the spectrum at T < 2 K. We find that its binding energy scales as 0.1e(2)/l, where l is the magnetic length, and it crosses the singlet slightly above 15 T.