Imagine storing the entire iTunes library of 35 million songs on a device the size of a credit card. Though it’s not yet possible, it may be someday – thanks to a recent study by nanoscientists at IBM Research – Almaden in San Jose, Calif. that was published in Nature. In the paper, the nanoscientists demonstrated the ability to read and write one bit of data on one atom. For comparison, today’s hard disk drives use 100,000 to one million atoms to store a single bit of information.
How it Worked
The most basic piece of information that a computer understands is a bit. Much like a light that can be switched on or off, a bit can have only one of two values: 1 or 0. Until now, it was unknown how few atoms it would take to build a reliable magnetic memory bit.
In this study, nanoscientists created the world’s smallest magnet, a single atom. Similar to a magnet on a refrigerator, this one had a north and south magnetic pole, but consisted of just a single atom of the element holmium. The single holmium atom was attached to a carefully chosen surface, magnesium oxide, which made its north and south poles hold in a stable direction even when disturbed, for example, by other magnets nearby. The two stable magnetic orientations defined the 1 and 0 of the bit. A sharp metal needle of a custom microscope (the IBM-invented, Nobel prize-winning scanning tunneling microscope) introduced a current that flipped the magnetic north and south poles of the atom and thus changed it between 1 and 0. This corresponded to the “write” process in a hard-disk drive. The IBM nanoscientists could then measure the magnetic current passing though the atom to determine whether its value was 1 or 0. This was the “read” process.
Meet the Researchers
Christopher Lutz is no stranger to innovation. At the age of nine, he declared to his parents, both artists, “I think I’m going to be a physicist.”
Yet, Chris started his academic career as a computer scientist. In 1985, out of money and energy, Chris took a leave from his UC Santa Cruz doctoral program and took a chance on a summer job at IBM Research – Almaden. Chris built a parallel computer to simulate the physics of atoms, satisfying his childhood quest. Eventually, Chris teamed up with renowned nanoscientist and IBM fellow, Don Eigler. Later joined by Andreas Heinrich, now at the Center for Quantum Nanoscience in Seoul, they published a stream of research throughout the past 25 years that employed their ability to move individual atoms. They also created the world’s smallest movie, dubbed “A Boy and His Atom,” a stop-motion animation using a sequence of images assembled from individual atoms.
Chris’s passion for nanoscience comes from his unique perspective on the world. “When I view the world, I see a series of computations,” said Chris. “For example, a leaf falling from a tree performs many computations in the process of falling. On a coarse scale, its motion takes into account the pull of gravity and resistance of the air to determine the speed of falling. Look closer and the motions of the atoms perform intricate computations in order to follow the laws of physics. My work at IBM centers on finding ways to understand the patterns in the tiny world of atoms and how to steer them towards doing the computations we want. For example, we made the world’s smallest interconnected logic gates by using precise arrangements of molecules. In this most recent study, a single atom performed an essential part of computation: storing a bit of data for us.”
To date, Chris has published dozens of nanoscience studies, several of which have made their way into university curricula worldwide. Kai Yang, a post-doctoral researcher at IBM, who now works with Chris, knows this first hand. Originally from a small city in China, Kai studied IBM’s nanoscience research at his local university. At one point, when he heard that members of the IBM Research nanoscience team were visiting his college campus, he
eagerly volunteered to serve as the team’s campus tour guide so he could become acquainted with his textbook heroes. That tour led to Kai landing an internship at IBM Research’s Almaden lab, where he worked with Chris Lutz and the team on the one-bit-on-one-atom study.
According to Kai, this was the research study that almost wasn’t. After one month of attempting to measure two stable magnetic orientations of the holmium atoms, the team had not yet succeeded. The team gave itself six weeks to prove the holmium atom is a stable magnetic bit − otherwise the study would be concluded. Convinced he could make it happen, Kai and his team, including visiting scientist Fabian Natterer, literally worked in the lab day and night to show it could be done by the impending deadline. Finally, at 4 a.m. in the lab one early morning, the team was able to demonstrate the two stable magnetic orientations of a single holmium atom. The key was realizing that the atom was so stable that they had to actively switch it between the states, by running a pulse of electrical current through it. This was the result that they eventually published in Nature.
“I’m glad we didn’t give up,” said Kai, who has recently been hired at IBM as a post-doctoral researcher and nominated to MIT Tech Review’s 35 Innovators Under 35 list based on his landmark work.
The IBM nanoscientists continues to explore the magnetism of individual atoms and the ways in which they interact, by arranging them precisely on a surface into structures that would not otherwise exist. The magnetic properties are sensed using their powerful new technique of single-atom spin resonance, which uses the same physics as MRI imaging, but applied to individual atoms.