Massless particle finally detected

New York, July 17 (IANS) Researchers have observed existence of a phenomenon that physicist Hermann Weyl predicted in 1929 – a kind of massless particle that features a singular point in its energy spectrum called the “Weyl point”.

The result could lead to new kinds of high-power single-mode lasers and other optical devices.

For decades, physicists thought that the subatomic particles called neutrinos were, in fact, the massless particles that Weyl had predicted — a possibility that was ultimately eliminated by the 1998 discovery that neutrinos do have a small mass.

“Every single paper written about Weyl points was theoretical, until now,” said study senior author Marin Soljaci, professor of physics at Massachusetts Institute of Technology (MIT).

The results appeared in the journal Science.

The elusive points can be thought of as equivalent to theoretical entities known as magnetic monopoles, study lead author Ling Lu, research scientist at MIT said.

These do not exist in the real world: They would be the equivalent of cutting a bar magnet in half and ending up with separate north and south magnets, whereas what really happens is you end up with two shorter magnets, each with two poles.

The achievement was made possible by a novel use of a material called a photonic crystal, the researchers said.

They calculated precise measurements for the construction of a photonic crystal predicted to produce the manifestation of Weyl points — with dimensions and precise angles between arrays of holes drilled through the material, a configuration known as a gyroid structure.

This prediction was proved correct by a variety of sophisticated measurements that exactly matched the characteristics expected for such points.

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