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Feynman diagrams are an important tool in modern theoretical physics, with applications in solid-state, high-energy physics, and quantum chemistry. Doc. dr. Denis Golež from the Department of Theoretical Physics and his colleagues from the Flatiron Institute (USA), Berkeley University (USA) and the University of Örebro (Sweden) discovered a new approach for using Feynman diagrams in quantum materials, published in Physical Review X. Higher-order Feynman diagrams are challenging in strongly correlated quantum systems due to their computational complexity. This study uncovered a 'hidden structure' within these high-order diagrams based on the separability of quantum propagators, see figure, significantly reducing computational demands. The algorithm was applied to non-perturbative problems where traditional quantum Monte Carlo methods would fail, offering a promising new tool for diagrammatic computations. This theoretical advancement is expected to greatly facilitate the discovery of new quantum collective states, such as excitonic magnetism and spin glasses.

Researchers from the Department of Condensed Matter Physics (Venkata. S. R. Jampani, Miha Škarabot and Miha Ravnik) in collaboration with colleagues from Universities of Ljubljana, Sorbonne, Siegen and Luxembourg reported on the synthesis of water-based templating nanoscale thin films in Advanced Materials. These films are made from superglue (cyanoacrylate monomers) vapours and grow with a controlled rate of several nanometres per minute. Superglues (cyanoacrylate monomers) are otherwise well-known for their rapid reactivity, forming polycyanoacrylate chains that bond materials instantly. On the contrary, in this report the modulated polymerization of cyanoacrylates was introduced, which enable controlled growth of thin polymer films. Furthermore, the shape and color of the film are precisely controlled by the polymerization kinetics, wetting conditions, and/or exposure to patterned light. This study introduces simple, versatile and an eco-friendly approach analogous to existing chemical vapor deposition techniques. This approach facilitates the creation of water-templated films for gas encapsulation, liquid packaging, and in-situ chemical/biological cargo packaging.

Researchers and collaborators of the Extreme Conditions Chemistry Laboratory (ECCL) at the "Jožef Stefan" Institute (Klemen Motaln, Anton Kokalj, Kristian Radan, Mirela Dragomir, Boris Žemva and Matic Lozinšek), in collaboration with partners from the Institute of Physics of the Czech Academy of Sciences (Kshitij Gurung, Petr Brázda and Lukáš Palatinus), have for the first time successfully employed 3D electron diffraction on nanocrystals to determine the crystal structures of reactive xenon compounds. To accomplish this, the team developed a specialized procedure for handling and transferring extremely reactive and air-sensitive substances, ensuring their safe introduction into a transmission electron microscope. This method paves the way for structural analysis of other reactive and sensitive compounds and materials, particularly those for which single-crystal growth is challenging, rendering traditional X-ray diffraction methods ineffective. This study, funded by GA ČR and ARIS as part of the CEUS joint research project, was published in ACS Central Science, where it was highlighted on the cover. The American Chemical Society (ACS) also featured the research in a press release.

Researchers from the Department of Low and Medium Energy Physics of the "Jožef Stefan" Institute (Dr. Špela Krušič and Prof. Dr. Matjaž Žitnik) took part in the measurements and data analysis of the experiment, which was carried out by an international group of experts at the SCS beamline of the free electron laser facility EuXFEL in Hamburg. They measured the absorption of short pulses (15 fs) of X-ray light with a wavelength of > 1.3 nm when passing through a 100 nm thick copper foil in the vicinity of the L3 edge. The results show an interesting dependence on the intensity of incident light, which is reported in an article just published in the journal Nature Physics. Up to 5 TW/cm², the absorption spectrum was the same as already known from previous measurements with weak light, and at higher intensities up to 200 TW/cm², a strong pre-peak appeared due to reversibly saturated absorption into an empty 3d orbital of copper. Above this threshold light intensity, the clear structures around the edge of L3 began to disappear, until above 100 PW/cm² they completely disappeared and practically nothing in the spectrum indicated the position of the L3 edge.