2010 November

Terahertz goes magnetic: Controlling spins with ultrashort electromagnetic bursts

Tuesday, 23rd November 2010General science information, Publication highlights

Ein schneller Schalter für atomare Kreisel: Die Atome des Nickeloxids (blaue Kugeln) lassen sich als winzige Stabmagneten betrachten, weil ihre Elektronen ein magnetisches Moment (blaue Pfeile) erzeugen. Physiker sagen: Die Atome besitzen einen Spin. In dem Experiment verkippt das Magnetfeld eines Terahertz-Impulses (rot) die Spinachse, so dass sie zu torkeln (präzedieren) beginnt. The basic principle: Electrons (blue spheres) carry a spin that can be seen as a persistent rotation of the electron about its own axis, resulting in a magnetic moment (blue arrows). In the experiment, spins are kicked by an intense terahertz magnetic transient (orange waveform), leading to a precession about their equilibrium directions, similar to a spinning top.

Physikern gelingt es, den atomaren Spin im Takt von Billionstel Sekunden umzuschalten
Festplatten in unseren PCs speichern Daten, indem ein Schreib- und Lesekopf für jedes Bit einen kleinen Bereich auf ihnen magnetisiert. Beim Auslesen tastet der Magnetkopf die Magnetisierung ab. Ziel ist es, die magnetisierten Bereiche immer mehr zu verkleinern und die Schreib- und Auslesegeschwindigkeit zu erhöhen. Einer Forschergruppe unter maßgeblicher Beteiligung des Fritz-Haber-Instituts (FHI) der Max-Planck-Gesellschaft ist es jüngst gelungen, Atome in einem Festkörper eine Billion Mal pro Sekunde gezielt “umzuschalten.” Als Schalter dient den Wissenschaftlern Licht, genauer gesagt eine Terahertz-Welle. Zwar liegt eine praktische Anwendung noch in weiter Ferne, doch für die Grundlagenforschung eröffnen sich damit neue Perspektiven. mehr

(Nature Photonics, Advanced online publication. 21 November 2010 | doi:10.1038/nphoton.2010.259)

Weitere Auskünfte: Dr. Tobias Kampfrath

Scientists at the Fritz Haber Institute, along with their European collaborators, have succeeded in controlling the electron spin direction, which has heretofore been inaccessible. The experiment employs the so-called terahertz radiation (1 THz = 1012 Hz), which is currently attracting attention because of its use in body scanners in airports. Like many other applications, these scanners exploit the electric component of the terahertz wave. The present work shows that the magnetic component of terahertz radiation has important potential applications as well. They have reported their findings in the esteemed journal Nature Photonics. more…

(Published online: 21 September 2010 | doi:10.1038/nphoton.2010.259)

Further information: Dr. Tobias Kampfrath


VIDI grant awarded to Dr. Bas van de Meerakker

Tuesday, 2nd November 2010Miscellaneous

Fritz Haber Institute’s Dr. Bas van de Meerakker has been awarded the prestigious VIDI grant by The Netherlands Organisation for Scientific Research (NWO) for his research on “molecular collisions in slow motion”. The VIDI grant is part of the Innovational Research Incentives Scheme that aims to encourage young scientists to develop their own original lines of research. Van de Meerakker has been a group leader in the Molecular Physics department of prof. Gerard Meijer since May 2005 working on novel experiments for the electrostatic deceleration and trapping of molecules and free radicals; his work was recognized with the Otto Hahn Medal in 2007.

His future research plans, to be carried out at the Institute for Molecules and Materials (IMM) at the Radboud University Nijmegen in The Netherlands, will focus on collisions between slow-moving molecules. A collision experiment in which molecules are scattered off each other is one of the most fundamental approaches to learn something about the molecules and their mutual interactions. “Unusual events can occur between colliding molecules in the low-temperature regime”, says van de Meerakker, “as they are dominated by quantum effects”. Such studies should reveal the intimate details of chemical reactions that have so far remained elusive.

Van de Meerakker will move to IMM in April 2011 and start his work in the Molecular & Laser Physics group; “although I am happy to be returning to Holland, I have really enjoyed my time here at the FHI and in Berlin.”