An international team of scientists from Austria and the United States has created a new variety of strontium superatoms. For this purpose, the researchers used a combination of a Bose-Einstein condensate and atoms in which electrons are in a highly excited state. This was announced in a press release on EurekAlert !.
Physicists have cooled a cloud of strontium atoms to temperatures close to absolute zero. The result is a Bose-Einstein condensate in which all atoms can reach the lowest possible energy state. This is due to the fact that strontium is a boson, that is, it can be in the same quantum state as other bosons of the same kind. This distinguishes them from fermions, which include, for example, electrons that are unable to occupy the same energy state.
In the condensate, strontium atoms become identical (indistinguishable), that is, it is impossible to determine where which particle is located. The wave functions describing their position in space overlap, and the entire system begins to behave as a single whole. In this state, quantum effects can be observed with the naked eye, such as superfluidity.
The researchers irradiated one of the particles in the Bose-Einstein condensate with a laser, creating a Rydberg atom in which an electron is so far from the nucleus that 170 other strontium atoms could fit inside the orbit. This system is stable, since its total energy is less due to weak scattering of a highly excited electron by neutral atoms. According to scientists, a new form of matter, called the Rydberg polaron, can only exist at low temperatures, since the bond between atoms is very fragile.
