Spintronics aims for atomic memories
R Colin Johnson
12/16/2010 2:01 PM EST
PORTLAND, Ore.—Spintronics memories should store quantum information on the individual atoms, rather than electrons, according to University of Utah researchers. Led by professor Christoph Boehme, a team of researchers demonstrated how it's done by reading and writing spin onto phosphorus atoms in a silicon substrate, achieving a refresh time of 112 seconds—thousands of times longer than memories storing information on electron spin.
"Nuclear spins where we store information have extremely long storage times before the information decays," said Boehme. "Its spin isn't messed with by what's going on in the clouds of electrons around the nucleus."
To prove that atomic nuclei store spins more reliably than electrons, the Boehme group's experimental demonstration used a phosphorus-doped silicon chip measuring just 1 millimeter square. After supercooling the material to 3.2 degrees Kelvin, an intense magnetic field of nearly 8.6 Tesla aligned the spins of the phosphorus atom's electrons, which was then transferred to the nuclei by FM-band radio waves.
Up to 112 seconds later, the group was able to demonstrate that near-terahertz wavelengths could then be used to transfer the nuclei spins back onto the atom's electrons, allowing its value to be electrically read-out as a current. The researchers showed that the mechanism was reliable by reading and writing the phosphorus nuclei 2000 times. Next the researchers are going to try the same demonstration with a single phosphorus atom.
A phosphorus-doped one millimeter square silicon chip demonstrate how data can be stored in magnetic "spins" on the nuclei of phosphorus atoms.