Liquid Light circa 2021

 

Source: Daniel Falcao/Unsplash

Polaritons are hybrid particles made up of a photon strongly coupled to an electric dipole. Examples of such a dipole include an electron–hole pair in a semiconductor, which forms an exciton polariton, and the oscillating electrons at the surface of a metal, which creates a surface-plasmon polariton.

Said entities are the key to future practical applications of liquid light.

In 2017, a group of researchers from Polytechnique Montréal, Canada, and Italy’s CNR Institute of Nanotechnology teamed up to conduct an experiment that demonstrated that light can achieve a superfluid state at room temperature. Previous studies had already confirmed the possibility of light existing as a superfluid, but all previous experiments needed to use ultra-low temperatures near absolute zero to bind photons together strongly enough to for them to behave as molecules and turn into a superfluid.

During the 2017 experiment, an ultra-thin film made of organic molecules was sandwiched between two highly reflective mirrors, and this setup was further subjected to a 35 femtosecond (10⁻¹⁵ seconds) laser blast. This intense light-matter interaction led to the formation of a superfluid.

"The extraordinary observation in our work is that we have demonstrated that superfluidity can also occur at room temperature, under ambient conditions, using light-matter particles called polaritons.

JJ Ying/Unsplash

Why liquid light matters.

The production of liquid light at room temperature promises interesting developments in the field of electronics, healthcare, data science, and many other domains:

• The number of transistors installed on a semiconductor chip is widely described as increasing by a factor of two every two years (also known as Moore’s law). This growth is necessary to meet the growing demands in increased speed needed for fast data transfer. In 2016, researchers at the University of Cambridge created a polariton switch capable of conducting electro-optical signals at high speed. This liquid light-based device has the potential to overcome the physical and technical limitations faced with current transistor chips. 
• A research paper titled Phenomenological consequences of superfluid dark matter with baryon-phonon coupling, published in September 2018, theorizes that dark matter (85% matter in the universe is dark matter) is also superfluid. If this theory is proven correct, then there is a possibility that further research on liquid light (which is also a superfluid) may increase our understanding of dark matter and dark energy.

And so it goes - Kurt Vonnegut