Toward ultrafast spintronics

Electronics have advanced through continuous improvements in microprocessor technology since the 1960s. However, this process of refinement is projected to stall in the near future due to constraints imposed by the laws of physics. Some of these bottlenecks have already taken effect. For instance, the clock speeds of processors are have not exceeded a few gigahertz, or several operations per nanosecond, for the past 20 years, a limitation stemming from the electrical resistance of silicon. This has led to an increasingly urgent global search for superior alternatives to semiconductor electronics.

One of the leading candidates, spintronics, is based on the idea of carrying information via the spin of electrons. Using spin currents to convey information is an exciting prospect because it involves lower energy consumption than ordinary electric currents. There are, however, numerous practical difficulties to be overcome. One of the most serious is the spin injection problem, transferring a spin current from one material to another (e.g., from a magnetic metal to a semiconductor). This tends to scramble the spins, destroying the information they carry.

Now, a breakthrough in the speed and efficiency of spintronics has been achieved by a team of scientists from Nanyang Technological University (NTU), the National University of Singapore (NUS), and the Agency for Science, Technology and Research (A*STAR) in Singapore, as well as Los Alamos National Lab in the USA. They have shown that an ultrashort pulse of spin current, lasting less than a picosecond (one trillionth of a second), can be injected from a metal to a semiconductor with amazing efficiency, breaking the previous spin injection record by over 10000 times. These findings were described in a pair of papers recently published in the leading scientific journals Nature Physics and Advanced Materials.