Magneto-optical probe of the two-dimensional hole-system low-temperature ground states

Band-gap magnetophotoluminescence (PL) has been used to study a high-quality, low-density p-type GaAs-${\mathrm{Al}}_{\mathit{x}}$${\mathrm{Ga}}_{1\mathrm{-}\mathit{x}}$As single quantum well at millikelvin temperatures. Two PL lines associated with recombination in the quantum well are observed. The lower-energy line, present over the entire field range, displays intensity minima at integer quantum Hall states and a marked intensity falloff to a minimum value as the Landau-level filling factor is reduced to ν=1/3. The higher-energy line emerges in the extreme quantum regime ν<1, and shows an intensity maximum at ν=1/3. These intensity features are quenched with increased temperature. The results show remarkable similarities with optical studies of two-dimensional electron systems.