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Active control of quantum materials is highly desirable for a wide range of applications. Metastable hidden states, such as the one discovered a few years ago by researchers at the Department of complex matter at the Jožef Stefan Institute, offer completely new functionalities. However, the underlying mechanisms that lead to hidden states remains a largely open scientific topic. In a new study published on November 24 in Science Advances, prof. dr. Dragan Mihailović in collaboration with a group of researchers from Germany and USA, investigated coherent control of the transition to a metastable hidden quantum state in the quantum material 1T-TaS2. Using time- and angle-resolved photoemission spectroscopy (trARPES), electronic and collective excitations during the transition to the hidden state were investigated in real time. Using laser excitation with time-controlled pulses, they managed to coherently control the transition to the hidden phase, thus revealing the importance of collective excitations which helped elucidate the mechanism for this interesting phenomenon.

At the Marie Skłodowska-Curie Action (MSCA) Coordinators Info Day held on November 9, 2023, in Brussels, three selected MSCA ITN projects—EuPRAXIA-DN, FoodTraNet, and PERSEPHONe—showcased their experiences in fostering synergies with other projects and initiatives. Nives Ogrinc (Department of Environmental Sciences), coordinator of FoodTraNet, provided insightful perspectives on the project's experiences in synergies with other ongoing projects such as PROMEDLIFE and FishEUTrust, as well as engaging with industry stakeholders. With its primary aim of providing high-level intersectoral training in new and emerging techniques, including mass spectrometry for food quality, safety, and security, to a new generation of early-stage researchers (ESRs), FoodTraNet demonstrated how strategic collaborations contribute significantly to the project's success. Moreover, the Coordinators Info Day served as a dynamic forum where these projects not only shared their achievements but also paved the way for future cross-project collaborations, reinforcing the collective strength of the scientific community. A video can be found on YouTube.

Physicists from the Jožef Stefan Institute and Brookhaven National Laboratory (USA) describe an experiment, which for the first time reports the existence of individual polarons at very high temperatures in a crystal of TaS₂. They are able to detect the displacements of ions surrounding individual electrons as they move around in the crystal at very high temperatures on ultrashort timescales of 10⁻¹² seconds. Furthermore, as the temperature is reduced, they are able to follow their condensation into polaronic crystal states which retain the signature of individual polarons. At low temperatures, the resulting state is superconducting, but forms a quantum spin liquid at intermediate temperatures, whose signature is identified by symmetry of the polaronic lattice displacements. The work has wide implication in many areas of physics, while the pioneering method opens the way to the search of polarons in other important materials. The present material is known for its very interesting properties reported in numerous recent Science and Nature articles. The work was published in Nature Communications.

Andrej Zorko and Matjaž Gomilšek from the Condensed Matter Physics Department at the Jožef Stefan Institute have published a review paper Experimental signatures of quantum and topological states in frustrated magnetism in Physics Reports, together with co-authors from India and Germany. It provides an overview of recent advances in the field of quantum and topological states of materials that arise from magnetic frustration, such as spin ice (with magnetic monopole excitations), quantum spin liquids (potential platforms for robust quantum computers), and topological spin textures, such as skyrmions (for spintronic circuits — magnetic analogues of electronic circuits). Characteristic signatures of these exotic but elusive states are pointed out and the most suitable experimental characterization techniques are presented. The article also provides a comprehensive overview of possible future directions in the field and highlights its potential, both for practical applications and for addressing important open questions in contemporary condensed matter physics.