Binding energy of negative trions in a CdTe quantum well at high magnetic fields

Abstract

We present the results of numerical calculations of electronic states of an exciton (X) and of a trion (X−) in a CdTe quantum well for magnetic fields B up to 150T. Using variational method we estimate the binding energy of the free X− in the singlet state (z component of angular momentum Lz=0), as well the binding energy of the free X− in the triplet state (Lz=−ℏ). Recent experiments have shown that even up to B=44T the binding energy of the negative trion in a singlet state is greater than in the triplet state. We show, however, that the binding energies of these two states should cross one another at very high magnetic fields. Specifically, using material parameters typical for these experiments, we show that the crossing of these levels will take place at field Bc≈65T. The binding energy of free X− in the triplet state exceeding that of the singlet state for fields B>Bc.