Photoluminescence from fractional quantum Hall systems: Role of separationbetween electron and hole layers - art. no. 045304

The photoluminescence (PL) spectrum of a two-dimensional electron gas (2DEG ) in the fractional quantum Hall regime is studied as a function of the sep aration d between the electron and valence hole layers. The abrupt change i n the response of the 2DEG to the optically injected hole at d of the order of the magnetic length lambda results in a complete reconstruction of the PL spectrum. At d < <lambda>, the hole binds one or two electrons to form n eutral (X) or charged (X-) excitons, and the PL spectrum probes the lifetim es and binding energies of these states rather than the original correlatio ns of the 2DEG. At d > 2 lambda, depending on the filling factor v, the hol e either decouples from the 2DEG to form an "uncorrelated" state h or binds one or two Laughlin quasielectrons (QE's) to form fractionally charged exc itons hQE or hQE(2). The strict optical selection rules for bound states ar e formulated, and the only optically active ones turn out to be h, hQE* (an excited state of the dark kQE), and hQE(2) The "anyon exciton" hQE(3) sugg ested in earlier studies is neither stable nor radiative at any value of d. The critical dependence of the stability of different states on the presen ce of QE's in the 2DEG explains the observed anomalies in the PL spectrum a t v = 1/3 and 2/3.