Press release: A new method for storing ultra-short current pulses now developed

Nr. 56/2013 - 05.04.2013

An international team of researchers gains insight into the dynamics of ultrafast magnet-based processes

(pug) How fast can electrical currents be turned on and off? An international team of researchers affiliated with the University of Göttingen have investigated new possibilities for testing these limits in magnetic materials. The researchers succeeded in generating and manipulating current flows on a time scale of 100 femtoseconds – one femtosecond equals one millionth of a billionth of a second. The results have been published in the online edition of the prestigious scientific journal Nature Nanotechnology.

Elementary particles, many atomic nuclei and atoms with certain electron configurations have what is called spin, defined as the rotation of a body around its own axis. This property of the electrons gives us an alternative method for controlling currents – called "spin electronics or spintronics". The scientists developed a layer just a few nanometers thick where they were able to store and read out the ultra-short current pulses. Excitation by a short laser pulse is used to generate the spin current, which, thanks to its special properties and interactions with the metal it flows through, can be localised and stored.

In their study, the scientists from Göttingen, Berlin, Jülich and Uppsala showed that the metal ruthenium is a good storage medium. By contrast, the spins flow right through a layer of gold. After storage, the spin current can be converted into conventional electrical charge current. The current flow across the electromagnetic radiation it creates can be detected in the terahertz frequency range.

"Only with these ultra-short spin current pulses of 100 femtoseconds in length can long-wave electromagnetic waves be generated in the terahertz range", says the Göttingen physicist Professor Markus Münzenberg. "By using different materials like ruthenium or gold, we are able to control the spectrum of electromagnetic waves. At present, we are working on how we can actively influence this type of control." Electromagnetic waves in the terahertz range are compelling for ultrafast information technology and for developing novel light sources. Moreover, they are required for the accurate analysis of complex crystals and molecules critical for the development and production of pharmaceutical products.

Original publication: T. Kampfrath et al. "Terahertz spin current pulses controlled by magnetic heterostructures", Nature Nanotechnology 8, 256–260 (2013), doi: http://dx.doi.org/10.1038/NNANO.2013.43 .

Contact address:
Professor Markus Münzenberg
Georg-August University Göttingen
Physical Institute I
Friedrich-Hund-Platz 1, 37077 Göttingen
Phone +49 (551) 39-7604
E-mail: mmuenze@gwdg.de
Website: www.uni-goettingen.de/de/99100.html