The notion that light waves have an associated mass is a fact that intrigues many people. In the world of Physics, however, in addition to the scientific truth being well known, it is part of a field called quantum electrodynamics, which studies the way in which an immaterial object, such as light, interacts directly with matter.
Based on this paradoxical concept, that waves have mass, a group of researchers recently published a study in the journal Physical Review Research, where they report the discovery of a “recipe” to create a new quasiparticle, “interconnecting” two fundamental particles of light, photons, of different colors.
If the light were mixed, the result would be a mixed color, but in the experiment the two photons remain coupled to each other, behaving as if they were a single particle, a quasiparticle. The concept was created by Nobel winner Lev Davidovich Landau to describe a constituent of matter that behaves as if it were unique within collective states with many particles.
In this experiment, the concept of quasiparticle was attributed by the researchers after the photon-photon pair presented its own moment and its own energy, which allowed even its mass to be calculated: as predicted by the team, photon-photons are a thousand times lighter than electrons.
As soon as their physical existence was proven, the resulting new quasiparticles were named photon-photon polaritons, that is, quasiparticles born from the junction of electrons with photons, a field of studies that emerged in the 1980s called plasmonic, which studies the behavior of waves dense electrons.
Manipulating two “pieces” of light in the laboratory was only possible due to the development of micron-resonators, devices that allow light to be stored, forcing it to go around a small ring or plate.
The discovery of this quasiparticle should have practical applications in the development of optical and quantum communication systems, and in precise measurements of frequency, time and distance.