Crystal-field mediated electronic transitions of EuS up to 35 GPa

Abstract

An advanced experimental and theoretical model to explain the correlation between the electronic and local structure of Eu$$^{2+}$$ 2 + in two different environments within a same compound, EuS, is presented. EuX monochalcogenides (X: O, S, Se, Te) exhibit anomalies in all their properties around 14 GPa with a semiconductor to metal transition. Although it is known that these changes are related to the $$4f^7 5d^0$$ 4 f 7 5 d 0 $$\rightarrow$$ → $$4f^6 5d^1$$ 4 f 6 5 d 1 electronic transition, no consistent model of the pressure-induced modifications of the electronic structure currently exists. We show, by optical and x-ray absorption spectroscopy, and by ab initio calculations up to 35 GPa, that the pressure evolution of the crystal field plays a major role in triggering the observed electronic transitions from semiconductor to the half-metal and finally to the metallic state.