ASOMEA-IX organized by SFB 951 & SFB 1083

The meeting was jointly organized by SFBs 951 “Hybrid Inorganic/Organic Systems for Opto-Electronics (HIOS)” Berlin and SFB 1083 “Structure and Dynamics of Internal Interfaces”. It attracted more than 80 participants from Europe, Asia and America to the Black Forest. The meeting consisted of 30 talks and 48 posters.

The series of biannual ASOMEA-workshops began in 2001 as a meeting of Swedish and Japanese scientists working with spectroscopic techniques and theoretical modeling for a better understanding of organic electronic materials and related interfaces. In 2016 the scope of the workshop was widened to include the German community and the intention to focus on organic materials at advanced stages, in situ/operando techniques, and time-resolved spectroscopy to name just a few.

For more information visit https://asomea9.internal-interfaces.de/.

Outreach Research Publication on SFB 1083

Copyright Scientia.

In the October issue of Scientia an outreach research publication entitled “Collaborating to Study Interfaces in Miniaturised Materials” covers our collaborative research center.

Scientia is a bimonthly science communication publication. The goal is to connect science and society by presenting research in an understandable, informative and attractive way to the general public. The article outlines motivation, scientific goals and methods of SFB 1083 “Structure and Dynamics of Internal Interfaces”. It highlights several results of the first funding period.

The publication is also accessible as a “scipod”-audiobook.

Publication

SFB 1083 – Collaborating to Study Interfaces in Miniaturised Materials
Scientia (2018) DOI: 10.26320/SCIENTIA255

Lightwave-driven Dirac currents – Publication by B6 (Höfer/Wallauer) in Nature

Johannes Reimann, Jens Güdde and Ulrich Höfer together with a team led by Rupert Huber in Regensburg have taken band structure movies of electrical currents carried by Dirac electrons as they are driven by an intense THz wave.

Artistic view of the experiment (image by Brad Braxley parttowhole.com).

The investigated currents consist of spin-polarized electrons confined to the uppermost atomic layers of the topological insulator Bi2Te3. The electrons were observed to react in an in­ertia-free fashion to the driving field, whereas spin-momentum locking lifts scattering times abo­ve 1 ps. This scenario enables giant sur­fa­ce cur­rent densities and bal­­listic mean free paths of several 100 nm, exceeding values obtained in conventional materials by or­ders of magni­tu­de. Based on this discovery, it might be possible to realize new lightwave-driven electronics in the future, combining low power consumption and clock rates that exceed those of conventional semiconductor devices by a factor of 1000 and more.

Animation of photoemission snapshots of the topological surface state in Bi2Te3 showing the back and forth acceleration of Dirac electrons at optical clock rates by an intensive Thz electric field.

The work of the two groups and collaborators in Novosibirsk and Hiroshima not only merges two novel and promising concepts in physics – topology and lightwave electronics. It also combines the expertise of the Regensburg group to manipulate electrons in solids with intense single-cycle terahertz (THz) transients, with the capabilities of time and angle-resolved photoelectron spectroscopy (ARPES) developed in Marburg.  The experiment conducted in Regensburg represents the first an­gle-re­­sol­ved pho­to­emis­sion spec­tro­scopy with subcycle resolution. It allowed Reimann and coworkers to directly ob­ser­ve how the car­rier wave of a te­rahertz pulse ac­celerates Di­rac fermions in the band­ struc­tu­­re. The resulting strong re­distribution in mo­men­tum space was directly mapped out in an ultrafast movie (Figure on larger screens).

In future experiments, it will be explored whether the topological protection responsible for the long scattering times at the Bi2Te3/vacuum interface survives when the material is covered by a protective cap layer as this is a prerequisite for device application.

Publication

J. Reimann, S. Schlauderer, C. P. Schmid, F. Langer, S. Baierl, K. A. Kokh, O. E. Tereshchenko, A. Kimura, C. Lange, J. Güdde, U. Höfer, and R. Huber, Subcycle observation of lightwave-driven Dirac currents in a topological surface band, Nature (2018) DOI: 10.1038/s41586-018-0544-x

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See also:
Joint press release of the Universities of Regensburg and Marburg (in German).
Blog Post “Topology at Cyberspeed” by Ulrich Höfer.
Homepage of the Huber group in Regensburg.

Contact

Prof. Dr. Ulrich Höfer
Philipps-Universität Marburg
SFB 1083 project B6
Tel.: 06421 28-24215
EMAIL