Otto Hahn Medals for Benedikt Frieß and Tomce Runčevski.

Benedikt Frieß studied physics at the University of Würzburg including scientific stays at the Universities of Oxford and Stanford. He did his master project in the group of Prof. Dr. Alfred Forchel in Würzburg, working on self-assembled quantum dots in photonic crystal cavities. In 2010 he moved to the department of Prof. Dr. Klaus von Klitzing (group of Dr. Jurgen Smet) at the Max Planck Institute for Solid State Research.

Illustration of the self-organized ordering of electrons in stripe and bubble phases in a two-dimensional electron system.

During his doctoral studies he investigated the behavior of two-dimensional electron systems under the influence of a strong magnetic field in a regime which is dominated by the quantum Hall effect. In order to resolve the rich details of this regime, it is important to keep detrimental influences from the environment on the electron system at bay, for instance, by reducing the sample temperature and using high-purity crystals. Under such extreme conditions the interactions between electrons start to play a dominant role, which leads to the emergence of a variety of exotic electron phases, whose nature are so far poorly understood. Amongst the vast array of electronic states realized are those which impose a self-organized ordering of electrons into spatial patterns resembling either bubbles or stripes – so-called density modulated phases (see picture). With his PhD work Benedikt Frieß succeeded in expanding the knowledge of these and other intriguing electron phases in the quantum Hall regime. In his experimental investigations he took, for instance, advantage of the coupling of the electrons to the surrounding nuclear spin system in order to probe the microscopic structure of the stripe phase by means of nuclear magnetic resonance. In a second project he used surface acoustic waves to measure the conductivity and screening behavior of the electrons in the density modulated phases. For his successful work in the field of density modulated phases and spin physics in the quantum Hall regime Benedikt Frieß has now been awarded the Otto Hahn Medal.

Tomce Runčevski reads for bachelor and master degrees in chemistry from University of Ss. Cyril and Methodius in Skopje. During the studies he spent one semester at Leipzig University. He finished his undergraduate studies in 2011, and he was honored with the University’s golden medal for excellence. The same year, he started with his PhD at the Max Planck Institute for Solid State Research, together with Prof. Dr. Robert E. Dinnebier in the X-ray Diffraction group. In 2014 he completed his dissertation and continued in the same group as a postdoc.

Crystal structures of inorganic corrosion product (left) and organic active pharmaceutical ingredient (right).

The scientific work of Tomce Runčevski revolved around the method of synchrotron and laboratory powder diffraction, used to address problems in solid state chemistry. Firstly, he explored the limits of the technique in ab initio crystal structure solutions and refinements. Thereafter, he applied the method in situ to follow chemical reactions and physical processes occurring in the crystalline state. He was focused on diverse systems, ranging from building and construction materials to drugs and pharmaceuticals. To name a few, he studied carbonation and dehydration processes in cements and solved crystal structures that are now routinely used in the industry for qualitative and quantitative Rietveld analyses. Using powder diffraction, he visualized the molecular motions responsible for photoinduced macroscopic breaking of organic crystals. In the course of his studies of pharmaceuticals, he successfully linked the hydrogen-bonding network with the corresponding crystals size and shape. Recently, he contributed to the understanding of the thermo- and photo-salient (or jumping crystal) effects, which present a novel platform for clean energy conversion. For his research highlights, he is awarded with the Otto Hahn Medal.
Starting at July 2015, Tomce Runčevski will join University of California at Berkeley, where he will continue to work in the field of solid state and materials chemistry.

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