Temperature-dependent quasiparticle conduction bandstructure of the EuS monolayer

Abstract

The temperature-dependent quasiparticle band structure of aferromagnetic EuS monolayer is calculated using the s-f model whichcombines the one-electron band structure and a many-body modelevaluation. The one-electron part required for the many-bodycalculation was obtained from a TB-LMTO (tight-binding linear muffin-tin orbital) band-structure calculation.A suitable supercell with five layers of empty spheres was used inthe band-structure calculations to obtain the Bloch energies of themonolayer. We find striking correlation effects in thequasiparticle spectrum induced by the s-f exchange interaction andalso observe significant temperature effects in the spectrum. Wehave further calculated the quasiparticle spectrum of the bulk EuSusing the same s-f model in order to compare the results with thosefor the monolayer and to analyse the influences of the lowdimensionality on the quasiparticle spectrum of this system. Thebulk spectrum also exhibits significant correlation and temperatureeffects. The conduction bands of the monolayer as well as the bulkEuS show red-shift with respect to temperature and the magnitude ofthe red-shift is found to be larger for some bands in the bulk EuScompared to that of the monolayer.