Electronic excitation spectrum of an antiferromagnetic semiconductor (EuTe)

We study the electronic quasiparticle spectrum of an antiferromagnetic semiconductor, with a special application to EuTe. By use of the commonly accepteds-f model it is shown that the conduction band splits into two quasiparticle subbands, where this splitting persists in the paramagnetic region (TtextgreaterT n ), too. Shape, width and degree of overlapping of the two subbands are strongly temperature dependent and quite different for different types off-spin arrangements.—We present furthermore a critical classification of mean field treatments (“Zener model”), which neglect all spin exchange processes between conduction electrons and localized moments. Within our many body approach the lower conduction band edge of EuTe does not shift significantly with temperature, in agreement with the experiment, while the Zener model predicts a drastic red shift upon cooling belowT n .