Electron-hole binding in a quantum-dot lattice: Excitonic oscillator strength

We study the excitonic oscillator strength and energies arising from the binding of an electron and a hole interacting through an attractive potential in a tunnel-coupled quantum-dot lattice. The effect of interdot tunneling of the electron and the hole and their attraction on the exciton oscillator strength and exciton binding is evaluated in one-dimensional (1D) and two-dimensional (2D) lattices. For short-range interaction, we find that close packing of the quantum dots into a 2D lattice can result in a nearly abrupt loss of electron-hole binding and the oscillator strength in contrast with a 1D lattice, where the effect is gradual. Numerical application includes general electron-hole attraction in 1D lattices and on-site plus nearest-neighbor attraction in 2D lattices. The time-dependent behavior of the oscillator strength is also examined for 1D on-site attraction.