V001 / JSI

Researchers of the Department of Low and Medium Energy Physics at Jožef Stefan Institute: Janez Turnšek, Klemen Bučar, Andrej Mihelič, Špela Krušič and Matjaž Žitnik, report new experimental results in Physical Review Letters. Upon passage of intense resonant XUV light of the free-electron laser FERMI through millimeters thick helium gas at a few tens of millibars pressure, self-amplification of weak spontaneous decay from doubly excited state has been observed at the EIS-TIMEX beamline. Due to stimulated emission, the fraction of excited atoms emitting an XUV photon instead of an electron has significantly increased significantly. The effect of decay redirection together with the collimation of emitted light leads to 8 orders of magnitude larger number of XUV photons emitted in the forward direction. This result provides opportunity to test new theoretical models and encourages further research to improve the efficiency of XUV spectroscopy and contribute to the development of new coherent light sources at short wavelengths.

Researchers Abdur Rehman Anwar, Maruša Mur, Matjaž Humar from Condensed Physics Department of the Jožef Stefan Institute and coworkers from Aristotle University of Thessaloniki, Greece, have developed microlasers made entirely out of edible materials. The microlasers that can be embedded directly inside edible products, were designed as barcodes, or as sensors/indicators for various food-related parameters. Illuminating a food product, containing such microlaser(s), with a laser pulse, and measuring the emission spectrum enables remote measuring of pH, sugar concentration, etc. or reading encoded information e.g., on expiry dates and the food origin. The microlasers are entirely safe for consumption and do not alter the appearance or taste of food. The research on edible microlasers that could significantly enhance traceability, security and freshness monitoring of food, was published in Advanced Optical Materials, and had a significant media impact, with many media outlets publishing the story about edible lasers, including Science, Phys.org, Gizmodo and others.

Researchers from the University of Leeds and the Jožef Stefan Institute have presented new metal-organic structures for magnetic data storage with minimal energy input. In a study published in the prestigious journal Advanced Materials, they demonstrated a reorientation transition of the magnetic moment under the influence of molecular contacts with ferromagnetic films, resulting from competition between the perpendicular magnetic anisotropy induced by a heavy non-magnetic metal and the in-plane magnetic anisotropy caused by molecules. By changing the thickness of the ferromagnet or selecting the molecular overlay layer (C60 and various phthalocyanines), the transition temperature can be adjusted to around room temperature. Near the transition temperature, the direction of magnetization can be easily switched with a small energy input, either by electric current or optically, with a femtosecond laser pulse. The results indicate applications in heat-assisted magnetic recording technologies. Research into ultra-fast switching with short optical pulses was conducted by young researcher Jaka Strohsack and Assoc. Prof. Tomaž Mertelj from the Complex Materials Department at the Jožef Stefan Institute.

Asst. Prof. Matjaž Gomilšek from the Condensed Matter Physics Department at the Jožef Stefan Institute and the Faculty of Mathematics and Physics, University of Ljubljana has recently published a paper in Physical Review Letters, together with co-authors from the UK, Switzerland, Norway, Germany, Canada, and Japan. In the paper, they revealed a previously overlooked, “hidden” role of local chiral anisotropy in centrosymmetric topological magnets. Specifically, they found that local chiral anisotropy helps stabilize skyrmions and meron–antimeron pairs (different kinds of topological spin textures) in Gd2PdSi3, despite the material’s inversion symmetry, which precludes any global chirality. In their study, they combined atomistic simulations of magnetic ordering with measurements of polarized resonant X-ray scattering on Gd2PdSi3 at electron accelerators Diamond in the UK and PETRA III, DESY in Germany. The discovery represents an important step towards understanding centrosymmetric topological magnets, and greatly expands the possibilities for stabilizing topological spin textures in highly symmetrical materials.