Evidence of inter-layer interaction in magneto-luminescence spectra of   electron bilayers
  Magneto-luminescence studies in electron bilayers reveal the hallmarks of the even-denominator and other quantum Hall states in the intensities and energies of the inter-band optical recombination lines. In the presence of a small tunneling gap between the layers the magneto-optical emission from the lowest anti-symmetric subband, not populated in a single-electron picture, displays maxima at filling factors 1 and 2/3. These findings uncover a loss of pseudospin polarization, where the pseudospin describes the layer index degree of freedom, that is linked to an anomalous population of the anti-symmetric level due to excitonic correlations. The results demonstrate a new realm to probe the impact of inter-layer Coulomb interaction in quantum Hall bilayers. 
Ilirjan Aliaj, Vittorio Pellegrini, Andrea Gamucci, Biswajit Karmakar,   Aron Pinczuk, Loren N. Pfeiffer, Ken W. West
cond-mat.mes-hall