Ever since a small age, we are taught that atoms are the building blocks of matter and that they are too small to see with the naked eye. That being said, there is still a lot of empty space inside the atom scientists from Austria and the US filled in some of those gaps. This resulted in a new state of matter in the form of giant atoms filled with other atoms.
There is some space between the nucleus of the atom and the electrons orbiting it. The distance of this orbit depends on the type of atom in question. At several hundred nanometers wide, the Rydberg atom has earned its nickname as the giant atom. This is more than s thousand times the size of the hydrogen atom.
To test the idea whether these giant atoms can be stuffed with other atoms, researchers from TU Wien, Rice University and Harvard started with a Bose-Einstein condensate. This state is achieved when atoms are cooled to just slightly above absolute zero. This slows them down and they begin to clump together.
The starting point was a cloud of strontium atoms. Once cooled to the Bose-Einstein condensate, the team energized one of the atoms with the help of a laser which lifts a single electron in the atom to a highly-excited state. The electron starts orbiting the nucleus at a much greater distance creating a Rydberg atom.
The new orbit is so large that it is possible for other strontium atoms to fit inside. The team was able to cram 170 atoms inside a single Rydberg atom. But, this number is subject to change depending on the Rydberg’s radius and the density of the condensate.
The atoms do have interactions with each other but they are very weak. The Rydberg atom’s electron is not scattered by the neutral atoms in the path and the electron is not transferred into another state. On running computer simulations the team found the interactions were weak and they decreased the total energy of the system forming a bond between the giant atom and the smaller ones inside it.
“The atoms do not carry any electric charge, therefore they only exert a minimal force on the electron,” says Shuhei Yoshida, co-author of the study. “It is a highly unusual situation. Normally, we are dealing with charged nuclei, binding electrons around them. Here, we have an electron, binding neutral atoms.”
“For us, this new, weakly bound state of matter is an exciting new possibility of investigating the physics of ultracold atoms,” says Joachim Burgdörfer, co-author of the study. “That way one can probe the properties of a Bose-Einstein condensate on very small scales with very high precision.”
Even though the bond is weak, it still means that it is a new state of matter and that is a really exciting prospect.