IBM is again taking the lead in spintronics research. Researchers at IBM Zurich and scientists at ETH Zurich for the first time have shown that electrons can be programmed to spin in unison in a semiconductor in what is called a persistent spin helix.
Importantly, the research, which was published in the journal Nature Physics, demonstrated that synchronizing the electrons in this way extends the spin lifetime by 30 times to 1.1 nanoseconds—the same time it takes for an existing 1GHz processor to cycle. It is expected that this level of control over the spin of electrons could result in more energy efficient electronic devices.
In 2003, a theory was proposed that it was possible to lock the spin rotation of electrons. The IBM and ETH Zurich researchers have not only been able to confirm this theory but also demonstrated that electron spins move tens of micrometers in a semiconductor with their orientations synchronously rotating along a path—not unlike a couple dancing a waltz.
In explaining the electron spin with the waltz metaphor, Dr. Gian Salis of the Physics of Nanoscale Systems research group at IBM Zurich said: “If all couples start with the women facing north, after a while the rotating pairs are oriented in different directions. We can now lock the rotation speed of the dancers to the direction they move. This results in a perfect choreography where all the women in a certain area face the same direction. This control and ability to manipulate and observe the spin is an important step in the development of spin-based transistors that are electrically programmable.”
The researchers were able to achieve this feat by first setting up the ability to monitor the spins of the electrons using a time-resolved scanning microscope technique. The researchers were then able to induce the synchronous spin motion by carefully engineering the spin-orbit interaction—a mechanism that couples the spin with the motion of the electron.
While this research promises to bring a greater level of control to spintronics, this research is far from finding its way into our electronic devices any time soon. For example, the experiments performed by the IBM scientists were performed at 40 Kelvin (-233 C, -387 F)—a temperature not suitable for your tablet computer.
Dexter Johnson is a contributing editor at IEEE Spectrum, with a focus on nanotechnology.