Biexciton in 2D parabolic quantum dot in magnetic fields

Abstract

We theoretically study biexciton, exciton and charged excitons confined in 2D parabolic quantum dots in a magnetic field by using an unrestricted Hatree-Fork method. The energy and binding energy of exciton and biexciton are presented as a function of magnetic field which show their increase with increasing magnetic field, although small. Our results for the case of strong confinement in InAs/GaAs self-assembled quantum dots show that, while the binding energies of both exciton and negatively charged exciton are positive, the binding energies of the biexciton and positively charged exciton are negative indicating that biexcitons in this system are antibinding.

Biexcitons and quadrons in self-assembled quantum dots

“…The picture of a conventional biexciton-the coupling of two excitons-is replaced by a totally different picture of pair interactions among the four carriers. In our previous works [8][9][10] we showed that the nontrivial Coulomb effect in a small 2D InAs quantum dot supports a bound quadron rather than a traditional biexciton. However, the limitation of these studies is that only the ground states were investigated, and only in a small range of electron-to-hole confinement ratios.…”

“…We focus on self-assembled quantum dots where charged particles can be modeled as a 2D electron-hole system with parabolic potential. As in [8][9][10] we use the model of a system of interacting electrons and holes confined in a 2D quantum dot with a parabolic lateral potential in the presence of a perpendicular magnetic field ⃗ B∥z. Within the effective-mass approximation, for a system of N electrons and M holes (N = M = 2 for biexciton and quadron) the total Hamiltonian is written as…”

“…While biexciton is a traditional excitation, we recently showed [8][9][10] that there exists another excitation, also consisting of two electrons and two holes, which is not necessarily the same as the biexciton. Furthermore, we found that under certain conditions in quantum dots this new excitation can be more favorable than the biexciton.…”

“…A self-assembled semiconductor quantum dot [7] with parabolic confinement potential plays an important role in the study of excitons and their complexities [8][9][10][11][12][13][14][15][16][17][18][19][20]. Self-assembled quantum dots are mainly formed through strain-induced mechanisms.…”

“…A quadron [8][9][10] or a quatuor [12], in fact, is a system of two electrons and two holes which interact with one another equally. The picture of a conventional biexciton-the coupling of two excitons-is replaced by a totally different picture of pair interactions among the four carriers.…”