A new type of quasiparticle found in high-quality semiconducting crystals - termed a collexon - is the subject of a paper published this week in Communications Physics. Materials which support the existence of quasiparticles can exhibit unique optical features and unusual physical properties, which are of interest to both fundamental and applied sciences.
In microscopically complex systems made up of many different particles - like solid materials - the motions of each particle are intricate, being the product of various strong interactions with the surrounding particles nearby. To provide a simpler window into the behaviour and properties of these systems, physicists reimagine solids as if they instead contained weakly-interacting particles in free space. These ‘quasiparticles’ have different types, which can provide different insights into material properties.
Christian Nenstiel and colleagues substitute atoms in a gallium nitride semiconductor crystal with atoms of the element germanium. The authors are able to achieve high concentrations of atomic substitution while still maintaining the crystal’s original structure. The substitutions, however, change the physical properties of the crystal - increasing the concentration of free electrons in the solid. By analysing the absorption and emission of light by these specially-treated crystals, the authors observe what they believe are the increasing stabilisation of collexons with a rising density of the electron gas. They suggest that this may be a standard property of all semiconductors, providing that the same level of atomic substitution can be achieved.
If these findings become supported by theoretical work, collexons could be recognised as a common feature of semiconducting materials. With semiconductors being fundamental to modern technology, improving our understanding of their electronic structure could be beneficial to both theorists and experimentalists alike.