The Jahn-Teller and pseudo Jahn-Teller effect in materials science

Abstract

Defining materials science as a translation from microscopic foundations of matter to macroscopic performance in applications, this mostly review paper is devoted to the special features of matter with Jahn-Teller (JT) and pseudo JT (PJT) centers that makes it outstanding in the search of novel properties and applications as novel materials. There are three kinds of problems in this respect. The first is related to the difficulties in the use of computer simulation of observable properties (a methodology widely employed in materials science) in application to systems with dynamic JT and PJT effects. The second is due to the specifics of such systems in interaction with external perturbations, which contribute with a strong orientational effect that enhances the observable properties by orders of magnitude. The third kind of problems relevant to materials science is in the use of the JT and PJT effects in revealing the origin of structural properties of a relevant polyatomic system and working out methods to influence them in designing novel materials.The paper formulates these problems and provides for examples that demonstrate their importance. For the second group of problems, illustrative examples include flexoelectricity, permittivity, and electrostriction in systems with dynamical JT and PJT centers, and it is shown that the latter enhance the observable properties by several orders of magnitude. Also related to this group of problems are the magnetic-dielectric bistabilities in molecular systems and solids induced by JT and PJT effect, illustrated on molecules like CuF3 and crystals of the type LiCuO2. The third group of problems is shown by the already multiply used application of the PJTE to reveal the origin of distortions of planar configuration in 2D (graphene-like) and quasi-2D materials and to work out methods of restoration of their planar configurations by means of external perturbations.