Ferroelectric systems

A ferroelectric is any piezoelectric which satisfies the following two conditions: (1) it possesses at least two stable polarization states in absence of external electric fields (2) the polarization states can be switched by means of an external electric field. Ferroelectrics show a multiplicity of unique and favorable physical properties and are therefore extensively used for applications such as electro-optical and acousto-optical devices. In particular, they are employed for the fabrication of the optical waveguides investigated in the SFB-TRR142. Bulk and surface properties of ferroelectric crystals as well as the ferroelectric transition are conveniently investigated from an atomistic perspective. Thereby ground and excited state properties as well as the polarization reversal mechanisms (both in the volume material and in thin films) can be explained. In our group we employ the density functional theory to model different ferroelectrics, in particular LiNbO₃, KNbO₃ and BaTiO₃.