Magneto-optics of two-dimensional hole systems in the extreme quantum limit

We report photoluminescence measurements on low-disorder, dilute (p6×1010 cm-1), two-dimensional (2D) hole systems in GaAs/AlxGa1-xAs quantum wells at low Landau-level filling factors (). Near and below =1/3 we observe two additional lines in the spectra. One of these, appearing 0.8 meV below the main line, is similar to a line observed in 2D electron systems at very low (1/5), which has been attributed to the condensation of 2D electrons into a Wigner solid. The other, observed 4 meV below the main line, has no apparent counterpart in 2D electron systems. We interpret the data as consistent with the magnetic-field-induced localization of 2D holes, possibly into a pinned Wigner solid state.