Graviton: An Insight into a Particle with Gravitational Behavior

For decades, physicists have been searching for gravitons, the hypothetical particles thought to carry gravity. Although they had never been detected in space, particles like gravitons have now been observed in semiconductors. Using these to understand the behavior of gravitons could help unify general relativity and quantum mechanics, which have long been at odds.

“This is a needle in a haystack. [finding]. And the paper that started all this goes back to 1993. ” lauren pfeiffer at Princeton University. He wrote the paper with several colleagues. Aaron Pinchukdied in 2022 before finding any hint of the elusive particle.

Pinchuk's students and collaborators, including Pfeiffer, have completed the experiment they began discussing 30 years ago. They focused on electrons within a flat piece of the semiconductor gallium arsenide, which they placed in a powerful refrigerator and exposed to a strong magnetic field. Under these conditions, quantum effects cause electrons to behave in strange ways. The electrons interact strongly with each other, forming an unusual incompressible liquid.

Although this liquid is not gentle, it is characterized by collective motion in which all the electrons move in unison, which can lead to particle-like excitations. To investigate these excitations, the team illuminated the semiconductor with a carefully tuned laser and analyzed the light scattered from the semiconductor.

This revealed that the excitation contains a type of quantum spin that had previously been theorized to exist only in gravitons. This isn't a graviton itself, but it's the closest thing we've ever seen.

Liu Ziyu The professor at Columbia University in New York who worked on the experiment said he and his colleagues knew that graviton-like excitations could exist in semiconductors, but they needed to make the experiment precise enough to detect it. He said it took many years. “From a theoretical side, the story was kind of complete, but the experiments weren't really convincing,” he says.

This experiment is not a true analog of space-time. Electrons are confined in flat, two-dimensional space and move more slowly than objects governed by the theory of relativity.

But he says it is “hugely important” and bridges various previously underappreciated areas of physics, such as materials physics and the theory of gravity. Kun Yan from Florida State University was not involved in this study.

but, Zlatko Papik Researchers at the University of Leeds in the UK cautioned against equating the new discovery with the detection of gravitons in space. He said the two are equivalent enough for electronic systems like the one in the new experiment to serve as a testing ground for theories of quantum gravity, but they are not equivalent for all quantum phenomena that occur in space-time on a cosmic scale. It says no.

This connection between particle-like excitations and theoretical gravitons also yields new ideas about exotic electronic states, team members say. de Linjie At Nanjing University, China.