Research press release


Communications Physics

Communications Physics: New quasiparticle found in semiconductor crystals

高品位の半導体結晶中に見つかった新しいタイプの準粒子(“collexon”と命名された)について報告する論文が、今週のCommunications Physics に掲載される。準粒子を含む材料は、独特な光学的特徴と特異な物理的性質を有しており、基礎科学と応用科学の両面で関心を集めている。


今回、Christian Nenstielたちは、窒化ガリウム系半導体結晶中の原子をゲルマニウム元素の原子に置換した。Nenstielたちは、この結晶の当初の構造を維持しながら、高濃度の原子置換を実現した。ただし、この原子置換を行うと、結晶の物理的性質が変化し、固体中の自由電子の濃度が高くなる。次に、この特殊処理された結晶による光の吸収と放出の分析が行われ、電子ガスの濃度が上昇するにつれてcollexonの安定度が高まると考えられる現象が観測された。Nenstielたちは、この点について、同じレベルの原子置換が実現されれば、全ての半導体の標準的特性と考えてよいとしている。


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.

doi: 10.1038/s42005-018-0033-4


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