Theoretically speaking, a single atom could be made to represent one computer bit — a technological prospect that could lead to unimaginably small storage devices. But getting atoms to behave in the desired way is easier said than done. Until now.
Above: A scanning tunneling microscope showing single holmium atoms on a platinum surface. It's the first functional example of the elusive single-atom bit. Credit: KIT/T. Miyamachi
A team of researchers from Karlsruhe Institute of Technology (KIT), the Max Planck Institute of Microstructure Physics in Halle, and the University of Leipzig has been working to develop the next generation of magnetic data memory devices — radically advanced storage mediums that could result in ridiculously small computing devices. They could also make their way into quantum computers — devices that are powered by the unique properties of atomic systems.
But to get there, researchers will need to get atoms to sit still and behave. Specifically, they need to get atoms to stop spinning so wildly — at least for a long enough period of time to make a storage device useful. Prior to this current study, researchers could only pull off the feat by awkwardly clumping several million atoms together.
For the new experiment, the researchers placed a single holmium atom onto a platinum surface. Then, working at temperatures close to absolute zero, they measured the magnetic orientation of the atom using a scanning tunnelling microscope. Looking at it, the researchers saw that they actually managed to fix a single atom to the metal surface — keeping its spin stable — for more than 10 minutes.
This stabilized "magnetic moment" was realized by suppressing the impact of the environment on the atom. Normally, the atom and the electrons on the metal surface would interact quantum-mechanically, causing the system to destabilize. The combination of holmium, platinum, and frigid temperatures did the trick, disturbing the normal interactions of quantum systems; holmium and platinum are "invisible" to each other as far as spin scattering is concerned. Put another way, the magnetic moment was stabilized by combining several symmetries intrinsic to the system, including time reversal symmetry, the internal symmetries of the total angular momentum, and the point symmetry of the local environment of the magnetic atom.
And by doing so, the researchers kept the magnetic spin of the system stable for a period that's about a billion times longer than comparable atomic systems.
The next step will be in figuring out how to actually adjust the spin and write useful and retrievable information on to the system, which will likely be done using external magnetic fields. It would also be nice if they could figure out a way to do this in an environment that's not so cold — an accomplishment reminiscent of the recent quantum memory breakthrough.
Read the entire study at Nature: "Stabilizing the magnetic moment of single holmium atoms by symmetry."