Properties of biexcitons

S. A. Moskalenko

S.A. Moskalenko

S. A. Moskalenko

R. M�rz, Stefan Schmitt-Rink, H. Haug

Hideki Gotoh, Hidehiko Kamada, Tadashi Saitoh +2 more

Exciton-biexciton coherent coupling effects are examined in semiconductor quantum dots. The exciton absorption spectrum is measured with the microphotoluminescence excitation technique in a single InGaAs quantum dot. The spectrum changes from a Lorenztian-type line shape to an unusual dip-shaped line shape with increasing excitation intensities in a higher exciton state where there is a large oscillator strength between the exciton and biexciton states. The intensity dependence of the dip energy width clearly indicates that coherent Rabi oscillation occurs between the exciton and biexciton states. The absorption properties with excitation light of different polarizations show that the dip-shaped spectra only appear when there is a large biexciton state population with linear polarization. A theoretical analysis undertaken with the density matrix method agrees well with experimental results. This agreement reveals that exciton-biexciton coherent interactions lead to unusual absorption spectra and contribute crucially to the optical properties of quantum dots. The exciton-biexciton coherent effects provide a scheme for controlling four distinguishable states, which can be applied to a demonstration of quantum gate operations.

Vo Tinh, Nguyen Ba An

We extend a previous paper on biexciton normal squeezing to the case of k th power amplitude squeezing in a quantum interacting system of photons, excitons and biexcitons. We find that the k th power amplitude squeezing depends on the characteristics of the initial coherent biexciton while the normal squeezing does not. Both the direction of maximal squeezing and the squeezing degree are derived as explicit functions of k. Especially, the squeezing degree always decreases with increasing k regardless of the initial conditions. All these properties are examined numerically.