Berlin 2018 – scientific programme

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KFM: Fachverband Kristalline Festkörper und deren Mikrostruktur

KFM 27: Postersession KFM

KFM 27.13: Poster

Thursday, March 15, 2018, 15:00–17:00, Poster E

Wavevector dependent optical properties from wavevector independent ab initio conductivity tensor — •René Wirnata¹, Ronald Starke¹, Giulio Schober², and Jens Kortus¹ — ¹Institut für Theoretische Physik, TU Bergakademie Freiberg — ²Institut für Theoretische Festkörperphysik, RWTH Aachen

In ab initio materials physics it is common practice to consider the conductivity tensor σ(k,ω) in the optical limit, i.e. k → 0 . However, response functions are naturally functions of both wavevector and frequency. Using Universal Response Relations [1], we are able to construct e. g. a frequency and wavevector dependent dielectric tensor from a wavevector independent optical conductivity. Since the dielectric function and the refractive index are related by n² = ε , we can thus calculate ab initio ordinary and extra ordinary refractive indices, n_e(ω) and n_o(ω) , of birefringent materials that fit very well with experimental results from [2]. In fact, obtaining the scalar functions n_e(ω) and n_o(ω) from a dielectric tensor ε(k,ω) requires in the most general case a more sophisticated algorithm, which is already known in theoretical optics [3-4]. In order to illustrate the reliability of this approach for different materials types, we have chosen Si, TiO₂ and α -Quartz as examples for isotropic, birefringent and optically active crystals.

[1] R. Starke, G.A.H. Schober: Photonic.Nanostruc. 14 (2015)

[2] E. Palik: Handbook of Optical Constants of Solids (2002)

[3] H. Römer: Theoretische Optik, Wiley-VCH (1994)

[4] R. Starke, G.A.H. Schober: arXiv:1708.06330