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, nc approximately 3 x 10(5) cm(-1). Above nc we find considerable optical gain demonstrating compellingly the possibility of a one-dimensional quantum wire laser operation.