Quantum Magnetism Observed For First Time, Physicists Say

Using super-chilled atoms, physicists have for the first time observed a weird phenomenon called quantum magnetism, which describes the behavior of single atoms as they act like tiny bar magnets.

Quantum magnetism is a bit different from classical magnetism, the kind you see when you stick a magnet to a fridge, because individual atoms have a quality called spin, which is quantized, or in discrete states (usually called up or down). Seeing the behavior of individual atoms has been hard to do, though, because it required cooling atoms to extremely cold temperatures and finding a way to "trap" them.

The new finding, detailed in the May 24 issue of the journal Science, also opens the door to better understanding physical phenomena, such as superconductivity, which seems to be connected to the collective quantum properties of some materials.

The research team at the Swiss Federal Institute of Technology (ETH) in Zurich focused on atoms' spin, because that's what makes magnets magnetic — all the spins of the atoms in a bar magnet are pointed the same way.

To get a clear view of atoms' spin behaviors, the researchers had to cool potassium atoms to near absolute zero.

The scientists then created an "optical lattice" — a crisscrossing set of laser beams. The beams interfere with each other and create regions of high and low potential energy. Neutral atoms with no charge will tend to sit in the lattice's "wells," which are regions of low energy.

Once the lattice is built, the atoms will sometimes randomly "tunnel" through the sides of the wells, because the quantum nature of particles allows them to be in multiple places at the same time, or to have varying amounts of energy. [Quantum Physics: The Coolest Little Particles in Nature]

Another factor that determines where the atoms lie in the optical lattice is their up or down spin. Two atoms can't be in the same well if their spins are the same. That means atoms will have a tendency to tunnel into wells with others that have opposite spins. After a while, a line of atoms should spontaneously organize itself, with the spins in a non-random pattern. This kind of behavior is different from materials in the macroscopic world, whose orientations can have a wide range of in-between values; this behavior is also why most things aren't magnets — the spins of the electrons in the atoms are oriented randomly and cancel each other out.

And that's exactly what the researchers found. The spins of atoms do organize, at least on the scale the experiment examined.

"The question is, what are the magnetic properties of these one-dimensional chains?" said Tilman Esslinger, a professor of physics at ETH whose lab did the experiments. "Do I have materials with these properties? How can these properties be useful?"

This experiment opens up possibilities for increasing the number of atoms in a lattice, and even creating two-dimensional, gridlike arrangements of atoms, and possibly triangular lattices as well.

- Huffingtonpost.com