Many-body correlations of electrostatically trapped dipolar excitons

We study the photoluminescence (PL) of a two-dimensional liquid of oriented dipolar excitons in InxGa1-xAs coupled double quantum wells confined to a microtrap. Generating excitons outside the trap and transferring them at lattice temperatures down to T = 240 mK into the trap we create cold quasiequilibrium bosonic ensembles of some 1000 excitons with thermal de Broglie wavelengths exceeding the excitonic separation. With decreasing temperature and increasing density n less than or similar to 5 x 10(10) 1/cm(2) we find an increasingly asymmetric PL line shape with a sharpening blue edge and a broad red tail which we interpret to reflect correlated behavior mediated by dipolar interactions. From the PL intensity I(E) below the PL maximum at E-0 we extract at T < 5 K a distinct power law I(E) similar to (E-0 - E)(-vertical bar alpha vertical bar) with -vertical bar alpha vertical bar approximate to -0.8 in the range E-0 - E of 1.5-4 meV, comparable to the dipolar interaction energy.