This effect has, at least in theory, been anticipated for a very considerable amount of time. However, a team from the Vienna Center for Quantum Science and Technology (VCQ) at Vienna University of Technology, working in conjunction with researchers from the University of Innsbruck, has now successfully detected this unusual atomic connection. This contact can be utilized to affect atoms that are at extremely low temperatures, and it is possible that this phenomenon also plays a part in the formation of molecules in space.
An electrically neutral atom contains a positively charged atomic nucleus that is surrounded by negatively charged electrons. This arrangement creates a cloud-like structure that surrounds the atomic nucleus. “If you now switch on an external electric field, this charge distribution shifts a little bit,” explains Professor Philipp Haslinger, whose research at the Atominstitut at Vienna University of Technology is supported by the FWF START program. Professor Haslinger’s research is being conducted at the Atominstitut at Vienna University of Technology. “The positive charge is displaced slightly in one direction, and the negative charge is shifted slightly in the other direction,” the scientist explained. “As a result, the atom abruptly has a positive and a negative side, and it is polarized.”
This polarization effect can also be created with laser light because light is merely an electromagnetic field that can change exceedingly quickly. When a large number of atoms are situated in close proximity to one another, the laser light polarizes them all in precisely the same manner. This can result in positive atoms being positioned on the left and negative atoms being positioned on the right, or it can have the opposite effect. Both times, two neighboring atoms shift their opposite charges toward one another, which creates an attractive force between them.
According to Mira Maiwoger, who is the initial author of the paper and works at Vienna University of Technology, “This is a very weak attraction force, therefore you need to execute the experiment very precisely in order to be able to measure it.” When atoms have a great deal of energy and are traveling very swiftly, the attraction force between them disappears very instantly. Because of this, a cloud of extremely cold atoms was utilized.
First, the atoms are trapped and cooled in a magnetic trap on an atom chip. This method is a technique that was developed at the Atominstitut in the laboratory of Professor Jorg Schmiedmayer. After that, the mechanism that was holding the atoms is disengaged, and they are allowed to fall freely. The temperature of the atom cloud is less than a millionth of a Kelvin, which is considered “ultracold,” but it still possesses enough energy to grow as it falls. This growth of the atomic cloud is slowed down – and this is how the attractive force is measured – if the atoms are polarized with a laser beam during this phase. This causes an attractive force to be produced between them, which in turn slows down the expansion of the atomic cloud.
According to Matthias Sonnleitner, the person responsible for laying the theoretical groundwork for the experiment, “Polarising individual atoms with laser beams is practically nothing new. The most important thing to take away from our experiment, however, is that we were finally able to achieve our goal of polarizing many atoms together in a manner that was under our control, so producing a force of attraction that could be measured between them.”
Utilizing this attractive attraction is a further method for exercising control over cold atoms. But it could also be crucial in the field of astrophysics: “In the expanse of space, minor forces can play a huge effect,” says Philipp Haslinger. “Here, we were able to show for the very first time that electromagnetic radiation may induce a force between atoms, which may assist to shed fresh light on astrophysical scenarios that have not yet been explained.”