Rydberg polarons

Why in news?

An international team of physicists have successfully created a “giant atom” and filled it with ordinary atoms, creating a new state of matter termed “Rydberg polarons”. These atoms are held together by a weak bond and is created at very cold temperatures.


It uses ideas from two different fields: Bose Einstein Condensation and Rydberg atoms.

A BEC (Bose Einstein Condensate) is a liquid-like state of matter that occurs at very low temperatures. A BEC can be perturbed to create excitations which are akin to ripples on a lake. Here, researchers have used a BEC of strontium atoms.

Electrons in an atom move in orbits around the nucleus. A ‘Rydberg atom’ is an atom in which an electron has been kicked out to a very large orbit. These have interesting properties and have been studied for a long time.

In this work, researchers used laser light on a BEC of strontium atoms so that it impinges on one strontium atom at a time. This excites an electron into a large orbit, forming a Rydberg atom. This orbit is large enough to encircle many other strontium atoms inside it.

As the electron moves around many strontium atoms, it generates ripples of the BEC. The Rydberg atom becomes inextricably mixed with these ripples and forms a new super-atom called a ‘Rydberg polaron’.


A particularly interesting implication is for cosmology. Our universe is believed to be filled with a mysterious ‘dark matter’ which exerts a gravitational force on other matter.

Some theories of dark matter postulate that it is a cosmic Bose Einstein Condensate, perhaps composed of an as-yet-unknown type of particle. If we are indeed living in an invisible all pervading Bose Einstein Condensate, this experiment can suggest ways to detect it.