Quantum optics, excitons, and degenerate-state excitation in semiconductor nanostructures

Using a fully microscopic theory it is shown that quantum-optical excitation can be used to generate excitons in quantum-degenerate population states. For the example of a thermal source it is shown that resonant excitation directly converts photons into excitons with effectively no center of mass momentum. The generated quantum-degenerate state possesses long-range order, is very stable against perturbations, and should be observable via its unusual directional and density dependence in luminescence measurements.