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Action d'un champ magnétique sur les trions excitoniques dans les semiconducteurs

Abstract : The excitonic trions are moving bound states of an exciton and an electron or a hole in a semiconductor. Their binding energies are often small as resulting from variational calculations. Though original properties are expected due to their charge, their experimental identification may be difficult because the exciton, biexciton and trion lines are sometimes very close. We show how a constant magnetic field may be used to distinguish the trions from other excitonic complexes. Indeed, in the case of the exciton or biexciton, the motion of the centre of mass may be eliminated by means of a lamb gauge transformation because these complexes are neutral. However, in the case of the charged trions, only the motion in the direction of the field may be eliminated by means of an analog one gauge transformation. Generally speaking, the relative motion cannot be separated from the motion of the centre of mass in a plane perpendicular to the magnetic field. However, for not too high fields, htis latter is expected to be slow in comparison with the former. We therefore separate the two motion in the sense of the Born-Oppenheimer approximation. In this limit, the centre of mass of the trions behave like single charged particles so that additional Landau levels appear in the energy spectrum. Finally, we compute the relative energy by means of the variation method using a 34-term Hylleraas-type wave function and discuss the optical absorption. We show which the absorption coefficient presents a pics succession whose the maxima are in near Landau's levels. Indeed, it show a oscillatory magneto-absorption
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El Mustapha Feddi. Action d'un champ magnétique sur les trions excitoniques dans les semiconducteurs. Physique [physics]. Université Paul Verlaine - Metz, 1987. Français. ⟨NNT : 1987METZ007S⟩. ⟨tel-01775522⟩

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