Indirect-to-direct crossover of laterally confined excitons in coupled quantum wells

Lateral confinement of excitons in coupled double quantum wells can be tailored to control exciton interwell tunneling. An indirect exciton in a coupled asymmetric double quantum well under applied bias can be made a direct exciton by lateral confinement. Large changes in exciton ground-state energies and oscillator strengths occur at this crossover. This crossover provides a new signature for lateral-confinement effects on excitons in zero-dimensional nanostructures such as quantum dots and electron-hole double-layer systems in a strong magnetic field.