For the first time, scientists have succeeded to capture pictures of individual potassium atoms scattered on an optical lattice, providing them with a distinctive opportunity to see how they work with one another. While taking these images is an achievement in itself, the method could help scientists to better understand the circumstances necessary for individual atoms to come together and form unusual states of matter similar to super-fluids and superconductors.
Group member Martin Zwierlein from MIT said in a statement, "Learning from this atomic structure, we can understand what is actually happening in these superconductors, and what one should do to create higher-temperature superconductors, approaching confidently room temperature."
To take the images, the group took potassium gas and cooled it merely a few nano-kelvins, which is just above absolute zero. To put that into viewpoint, 1 nano-kelvin is -273 degrees Celsius, -460 degrees Fahrenheit. At this tremendously cold temperature, the potassium atoms become sluggish to a crawl, which let the group trap some of them inside a two-dimensional ocular lattice, a difficult series of intersecting lasers that can trap single atom inside different intensity waves.
Zwierlein said, "For us, these effects occur at nano kelvin because we are at work with diluted atomic gases. If you have a thick piece of matter, these similar effects may well happen at room temperature."
With the atoms stuck in the lattice, the group easily took hundreds of pictures using a high-resolution microscope to understand how the atoms arranged themselves. They discovered that in the parts of the lattice that were less dense, such as around the ends, the potassium atoms retained their distance from one another, making a bit of 'personal space' between every atom called a Pauli hole.
Zwierlein said, "They set up a little space for themselves where it is very impossible to find a second guy inside that space."
In the center of the lattice, where the gas is denser, they found that the atoms were expected to be super close together, sometimes on top of each other, and that they often concerned with themselves in by an arrangement of irregular magnetic orientations.
Zwierlein said, "These are stunning, anti-ferromagnetic connections, with a checkerboard arrangement up, down, up, down."
A good method to imagine this is to picture how human populations vary based on density.
For instance, in cities, people are totally cool with living above and below others, giving up plenty of their own space. While others, in fewer dense regions like the countryside, have too much space separating them from their neighbors.
The group completed their experiment to improve a better understanding of superconductivity, a quantum mechanical occurrence where there is zero resistance for electrons to move.
Since the technology does not yet exist for scientists to truly see electrons on a lattice, the group used potassium gas as a stand-in to discover the Hubbard-Fermi model, which tells how atoms will work with each other based off of electrons.
Zwierlein said, "That is a big reason why we do not understand high temperature superconductors, where the electrons are very intensely interacting."
"There is no standard computer in the world that can estimate what will happen at very low temperatures by relating electrons. Their three-dimensional correlations have also never been detected in situ, because no one has a microscope to look at each and every electron."
With more study, a better understanding of superconductivity might one day lead to the formation of electric structures that have zero resistance, making them much more effective than anything we have right now. The next stage is for the group to try and observe the similar atoms at an even lower temperature, to calculate how they function and if they can make a superconductor.
The study has been printed in Science.