Mott transition from a diluted exciton gas to a dense electron-hole plasma in a single V-shaped quantum wire

We report on the study of many-body interactions in a single high-quality V-shaped quantum wire by means of continuous and time-resolved microphotoluminescence. The transition from a weakly interacting exciton gas when the carrier density n is less than ${10}^5{\mathrm{cm}}^{-1}$ (i.e., ${\mathrm{na}}_X<0.1,$ with $a_X$ the exciton Bohr radius) to a dense electron-hole plasma $(n>\mathrm{}{10}^6{\mathrm{cm}}^{-1},$ i.e., ${\mathrm{na}}_X>1)$ is systematically followed in the system as the carrier density is increased. We show that this transition occurs gradually: the free carriers first coexist with excitons for ${\mathrm{na}}_X>0.1;$ then the electron-hole plasma becomes degenerate at ${\mathrm{na}}_X=\mathrm{0.8.}\mathrm{}$ We also show that the nonlinear effects are strongly related to the kind of disorder and localization properties in the structure especially in the low-density regime.