Modification of Zeeman states in a magnetic field and the alignment-orientation transition in triplet exciton emission in gallium selenide

The magnetic-field-induced optical alignment-orientation transition in a system of triplet bound excitons in a resonantly excited GaSe crystal has been studied using optical spectroscopy. It has been demonstrated that this effect can be assigned to a variation of the properties of Zeeman (spin) states of triplet excitons in a magnetic field, which initiates a change in the optical activity of these states in circularly and linearly polarized light. For the transition to become possible, the model requires that the electronic system of the crystal supports spin-orbit coupling. The approach employed permits the adequate description of experimental data, as well as calculation of the evolution of the effect during the bound-exciton lifetime.