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Scientists pinpoint exotic new particle

This liquid-like particle droplet is created by light and its energy (horizontal direction) has quantised dependency on light intensity (vertical direction) (Source: Brad Baxley )

In the field of quantum physics, you could call this a droplet in the bucket.

Physicists in Germany and the United States have discovered an exotic new type of particle that they call a quantum droplet, or dropleton.

Writing in the journal Nature, they say it behaves a bit like a liquid droplet and described it as a quasiparticle — an amalgamation of smaller types of particles.

The discovery, they add, could be useful in the development of nanotechnology, including the design of optoelectronic devices. These include things like semiconductor lasers used in Blue-ray disc players.

The microscopic quantum droplet does not dawdle. In the physicists' experiments using an ultra-fast laser emitting about 100 million pulses per second, the quantum droplet appeared for only about 2.5 billionths of a second.

That does not sound like much, but the scientists say it is stable enough for research on how light interacts with certain types of matter.

A previously known example of a quasiparticle is the excitation on, a pairing of an electron and a "hole" — a place in the material's energy structure where an electron could be located but is not.

The quantum droplet is made up of roughly five electrons and five holes. It possesses some characteristics of a liquid, like having ripples, the scientists write.

Quantum physics is a branch of physics that relates to events taking place on the tiniest scale. It is essential in describing the structure of atoms.

Particles are the basic building blocks of matter. They include things like subatomic entities such as electrons, protons, neutrons and quarks. Only rarely are new ones found.

The scientists in Germany worked with a team led by physicist Steven Cundiff at JILA, a joint physics institute of the University of Colorado at Boulder and the US National Institute of Standards and Technology.

It was in Boulder where the laser experiments were performed using a semiconductor of the elements gallium and arsenic, revealing the new particle, albeit fleetingly.

"Even though this happens so rapidly, it is still useful to understand that it does happen," says Cundiff.

Light applications

The scientists foresee practical value in the discovery.

"The effects that give rise to the formation of dropletons also influence the electrons in optoelectronic devices such as laser diodes," says physicist Mackillo Kira of the University of Marburg in Germany, one of the researchers.

Examples of optoelectronic devices include LED lights and semiconductor lasers used in telecommunications and Blu-ray players.

"For example, the dropletons couple particularly strongly to quantum fluctuations of light, which should be extremely useful when designing lasers capable of encoding quantum information," Kira adds.

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