Researchers at Columbia University have discovered the fastest and most efficient semiconductor to date. The new superatomic material discovered could lead to numerous speed and efficiency improvements throughout the industry.
The superatomic material, Re6Se8Cl2 binds with phonons when they come into contact, unlike other materials that scatter on contact. This binding creates a new quasiparticle called acoustic exciton-polarons which exhibit ballistic flow. In the study, published in Science, researchers discovered that the acoustic exciton-polarons in the new superatomic material move twice as fast as electrons in silicon. This speed allows them to cross several microns in less than a nanosecond.
Because the quasiparticles are controlled with light instead of electrical current, theoretical processing speeds of the particles could reach femtoseconds while at room temperature. “In terms of energy transport, Re6Se8Cl2 is the best semiconductor that we know of, at least so far,” said Milan Delor, professor of chemistry at Columbia University.
When the researchers began looking at Re6Se8Cl2, they did not expect to discover a faster semiconductor. The team began using the material to test their microscope's resolution as the material should not have conducted very much. “It was the opposite of what we expected,” said Delor. “Instead of the slow movement we expected, we saw the fastest thing we’ve ever seen.”
Once the observations were made, the team proceeded to develop an advanced microscope that they could use to directly image polarons as they form and move throughout the material. Further analysis led to the discovery that the speed of the quasiparticles is related to how slow they move. In silicon, particles can move extremely fast but they tend to bounce around and do not make it very far. The excitons in Re6Se8Cl2 are comparatively very slow, but it's this slow speed that allows them to meet and pair with acoustic phonons. The resulting quasiparticles formed are heavy and unimpeded by other phonons, leading them to move faster than electrons in silicon.
“This is the only material that anyone has seen sustained room-temperature ballistic exciton transport in. But we can now start to predict what other materials might be capable of this behavior that we just haven’t considered before,” said Delor. “There is a whole family of superatomic and other 2D semiconductor materials out there with properties favorable for acoustic polaron formation.”