Excitons in a high magnetic field

Sammanfattning: The interaction of excitons with each other and with charged impurities has been studied in a high magnetic field when the distance between the Landau levels is greater than the Coulomb unit of energy, in the frame of the model suitable for description of Wannier excitons in semiconductors. The analytical expressions for the pair interaction potential between hydrogenlike excitons in a high magnetic field are derived for the triplet and singlet terms. It is shown that the ground state of excitonic molecule in a high magnetic field is the triplet term 3IIu which corresponds to the case when one exciton is in the ground state and the other is in the first excited state. The effects of electron (e) and hole (h) g-factors and finite values of a magnetic field are considered. Probable explanation of some features of the excitonic spectrum observed in experiments with germanium placed in a magneticfield is given.The interaction of excitons with impurities, as well as with each other, in two-dimensional quantum well semiconductor structures drastically depends on the existence of the e - h-symmetry. It was found that different kind of transitions with spin-singlet-spin-triplet oscillations and increasing the total angular momentum, the magnetic induced binding and evaporation of impurity bound states of e - h complexes can take place for systems with spatially separated electron-hole layers when the magnetic field increases. The nature of the ground state in the presence of impurities as well as the possible implications of the results in experiments are discussed.