Particle Physics: 'Mind-Bending' Negative Mass Device Reveals New Way to Create Lasers

Illustration of confined light interacting with an atomically thin semiconductor to create particles with negative mass. Michael Osadciw/University of Rochester

Physicists have designed the first device to create particles with charged negative mass. The breakthrough could lead to an entirely new way to generate laser light using only a tiny amount of energy.

The success hinged on making a device that allowed for the creation of strange particles called polaritons. For the device, researchers at the University of Rochester positioned two mirrors to form an "optical microcavity." Inside that space, light is held at different colors of the spectrum depending on how the mirrors are arranged, according to a press release from the University of Rochester.

The researchers outfitted the microcavity with a semiconductor made from two chemical elements, one that is metallic and one that is not. This particular semiconductor was about the width of an atom, which is more than a million times smaller than a human hair. The semiconductor was strategically placed to interact with the trapped light. This interaction generated tiny exciton particles from the semiconductor that then combined with photons from the light. This mixing formed new, hybrid particles called polaritons, some of which have negative mass. A paper describing the research was published in the scientific journal Nature Physics.

Negative mass is hard to grasp mentally—and also physically. It's matter that acts the exact opposite of however you'd assume it would. Anything an object would be expected to do when some kind of force is applied, an object with negative mass does the inverse.

"That's a kind of mind-bending thing to think about," co-author Nick Vamivakas said in the press release, "because if you try to push or pull it, it will go in the opposite direction from what your intuition would tell you." Such matter is part of the theory behind how wormholes might work.

But these properties don't negate the more familiar laws of physics. "People have been asking me if 'negative mass' means instead of falling because of gravity the device would float. That's not what this means," Vamivakas, an associate professor of quantum optics and quantum physics at Rochester's Institute of Optics, told Newsweek. "Negative mass is a property of the particles withinthe material. The material still has mass; if I take my hand off it, it'll fall to the floor."

The physicists believe polaritons could lead to cheap, efficient methods for conducting electricity. Because the bizarre particles they've created have charges associated with them, they can be manipulated to push and pull an electric field.

Vamivakas said he and his colleagues are hoping to use the device to create lower-power lasers, meaning lasers that don't need to expend a great deal of energy to generate the same amount of light. Various reports of negative mass have been made in recent years, some of which were subsequently contested. What sets this research apart is that it resulted in polaritons with electrical charges, said Vamivakas, whose lab the work was conducted in. All other demonstrations of negative mass he's aware of used uncharged particles, which wouldn't facilitate such experiments with lasers.

"We want to push the envelope of how efficient things can be," Vamivakas said. "The particles are somewhat light-like, so they move around faster in a material than normal electrons. We're trying to come up with ways to make switches, to use negative-mass particles to turn things on and off in a clever way."