EXAFS study of ferroelectric topological crystalline insulators

The topological crystalline insulators (TCI) are materials with a topologically nontrivial band structure protected by a crystalline symmetry. One of the TCI materials is Pb1-xSnxTe which undergo transition from normal to inverted band gap structure with composition changing. The optical and magnetooptical measurements show ferroelectric transition at temperature of about 30-100K for Sn concentration of 30-60%. On the other hand, the temperatue dependent x-ray diffraction does not show structural change. Our goal is to study (Pb,Sn)Te thin films by EXAFS to check local atomic displacements below transition temperature. The results will explain the nature of the observed phase transition. The results will be comparted with (Pb,Ge)Te alloy layers, which are known to be ferroelectric.