Scientists have discovered that a 'superatomic' material is the fastest and most efficient semiconductor of all time.
Semiconductors are the basis for structures ranging from transistors to supercomputers. Researchers at Columbia University have identified a new semiconductor material that appears to outperform known semiconductors. The material, called Re6Se8Cl2, consists of a mixture of rhenium, selenium and chlorine, whose atoms form clusters that behave like a single, large atom - a 'superatom', which is the reason for its speed as a semiconductor. In each material, its atomic structure emits tiny vibrations that travel as special quantum particles (called phonons), which can scatter high-energy particles such as electrons or excitons. This energy is quickly lost in the form of heat, a constant challenge in the development of electronic circuits and systems. However, Re6Se8Cl2 has a special position here. Its excitons do not scatter when they are hit by phonons, but bind to them and thus form a different form of quasiparticle: acoustic exciton polarons. Although these can still transport energy, they move much more slowly than normal excitons and, contrary to expectations, this leads to higher speeds than in silicon. The team compares this phenomenon to the old story of the tortoise and the hare. Electrons can move very fast through silicon, but they tend to move in all directions, which is not the most efficient way. The polarons in Re6Se8Cl2, on the other hand, are slower and are not affected by other phonons, so they move further and more smoothly. The scientists found that the polarons in Re6Se8Cl2 ultimately travel about twice as fast as electrons in silicon. As they can be controlled by light rather than electricity, the researchers believe that if electronic devices were theoretically made using this material, they could be six orders of magnitude faster than existing devices today. In terms of energy transport, Re6Se8Cl2 is the best semiconductor known to date, according to Milan Delor, one of the authors of the study. However, the material is not expected to find its way into the electronics industry in the foreseeable future. On the contrary: the team considers it unlikely that this 'superatom' cluster in particular will ever come onto the market. Rhenium is too rare and too expensive for consumer goods. However, now that the researchers have proven the concept itself, they are convinced that similar and hopefully cheaper materials could exhibit comparable behavior. Their basic research paves the way for the investigation of a whole range of 'superatomic' semiconductor materials. The research has been published in the journal Science.
