Eur. Phys. J. B (2017) 90: 29
https://doi.org/10.1140/epjb/e2017-70623-9

Regular Article

Ab-initio optical properties and dielectric response of open-shell spinel zinc ferrite

Mulliken Center for Theoretical Chemistry, University of Bonn, 53115 Bonn, Germany

^a e-mail: ziaei@thch.uni-bonn.de

Received: 19 October 2016
Received in final form: 23 December 2016
Published online: 6 February 2017

Abstract

In the present work, we predict the optical properties and the dielectric response spectrum of the spinel zinc ferrite Zn₂Fe₄O₈, and show in particular the impact of many-body effects on the absorption spectrum, using advanced many-body perturbation approach. The excitonic effects remarkably redistribute the spectral weights causing a red-shift of 1.6 eV of the maximum of the independent particle G₀W₀ (IP-G₀W₀) towards the electron-hole affected spectrum. The excitation spectrum of the zinc ferrite exhibits a low lying doubly degenerated bound dark exciton at 1.84 eV with a fully symmetric excited-state density, and a narrow optical gap setting on at 1.93 eV. We further analyse the electronic transitions and exciton density distributions giving insights to the nature of excitations. The dielectric response of Zn₂Fe₄O₈ shows a particular sensitivity to the excitations higher than the electronic band gap, however it abruptly becomes passive to the incoming electro-magnetic wave and propagates to the negative regions at high energy regimes.