Material Map of Phase Change Materials - Localization of Delocalization

  Map of phsae change materials. I. Physikalisches Institut Map of different materials. Marked in green are phase change materials. Published in Nature Materials.

Phase change materials excel with a strong contrast between an amorphous and crystalline phase. Due to limited understanding of the intricacies of phase change materials the search for new materials is dominated by large-scale test series. We aim to realize a systematic and extensive classification of this material class. For this matter we search for appropriate parameters that play a critical role in the occurrence of the typical properties of phase change materials.

  Resonant bonding in comparison to covalent bonding I. Physikalisches Institut Resonant bonding in GeTe. Resonant bonding with delocalized electrons (middle) is energetically favorable to covalent bonding (left, right).

A known phenomena related to the phase transition in this systems is the occurrence of the so-called resonant bonding. This bonding type features a delocalization of electrons in the binding orbitals as is observed for example in benzene and is strongly dependent on the disorder of the system. Consequently, understanding the cause for disorder is critical for a better understanding of phase change materials as well as a clear identification and distinction of this material class.

With the help of numerous measuring methods we try to learn more about the properties of these materials. Transport measurements give us information about the band structure and energy levels of the conduction carriers while diverse x-ray and optical methods let us research structure and bonding behavior. With a combination of distinct techniques we have access to promising and exciting opportunities for researching phase change materials.