Many-Body Renormalization of Semiconductor Quantum Wire Excitons: Absorption, Gain, Binding, and Unbinding

We consider theoretically the formation and stability of quasi-one-dimensional many-body excitons in GaAs quantum wire structures under external photoexcitation conditions by solving the dynamically screened Bethe-Salpeter equation for realistic Coulomb interaction. In agreement with several recent experimental findings the calculated excitonic peak shows weak carrier-density dependence up to (and even above) the Mott transition density, $n_c\sim 3\times {10}^5{\mathrm{cm}}^{-1\mathrm{}}$. Above $n_c$ we find considerable optical gain demonstrating compellingly the possibility of a one-dimensional quantum wire laser operation.