The coherent infrared and THz sources driven by the superconducting electron accelerator ELBE are described. The present status of the facility is summarized and a few scientific highlights are mentioned. Finally plans for a successor facility (Dresden Advanced Light Infrastructure, DALI) are outlined along with the most important scientific and technological challenges. Graphical

The integration of heterogeneous modular units for building large-scale quantum networks requires engineering mechanisms that allow suitable transduction of quantum information. Magnon-based transducers are especially attractive due to their wide range of interactions and rich nonlinear dynamics, but most of the work to date has focused on linear magnon transduction in the traditional system composed of yttrium iron garnet and diamond, two materials with difficult integrability into wafer-scale quantum circuits. In this work, we present a different approach by using wafer-compatible materials to engineer a hybrid transducer that exploits magnon nonlinearities in a magnetic microdisc to address quantum spin defects in silicon carbide. The resulting interaction scheme points to the unique transduction behavior that can be obtained when complementing quantum systems with nonlinear magnonics.

We study the photoinduced metallization process in niobium dioxide ${\mathrm{NbO}}_2$. This compound undergoes the thermal insulator-to-metal transition at the remarkably high temperature of 1080 K. Our optical pump-terahertz probe measurements reveal the ultrafast switching of the film on a subpicosecond timescale and the formation of a metastable metallic phase when the incident pump fluence exceeds the threshold of $\sim 10\mathrm{mJ}/\mathrm{c}{\mathrm{m}}^2$. Remarkably, this threshold value corresponds to the deposited energy which is capable of heating ${\mathrm{NbO}}_2$ only up to 790 K, thus, evidencing the nonthermal character of the photoinduced insulator-to-metal transition. We also observe an enhanced formation of the metallic phase above the second threshold of $\sim 17.5\mathrm{mJ}/\mathrm{c}{\mathrm{m}}^2$ which corresponds to the onset of the thermal switching. The transient optical conductivity in the metastable phase can be modeled using the Drude-Smith model confirming its metallic character. The present observation of nonthermal transition evidences a leading role played by electronic correlations in ${\mathrm{NbO}}_2$ and can serve as an important test bed for understanding photoinduced phenomena in strongly correlated oxides.

Van der Waals magnetic materials are an ideal platform to study low-dimensional magnetism. Opposed to other members of this family, the magnetic semiconductor CrSBr is highly resistant to degradation in air, which, in addition to its exceptional optical, electronic, and magnetic properties, is the reason the compound is receiving considerable attention at the moment. For many years, its magnetic phase diagram seemed to be well-understood. Recently, however, several groups observed a magnetic transition in magnetometry measurements at temperatures of around 40 K that is not expected from theoretical considerations, causing a debate about the intrinsic magnetic properties of the material. In this Letter, we report the absence of this particular transition in magnetization measurements conducted on high-quality CrSBr crystals, attesting to the extrinsic nature of the low-temperature magnetic phase observed in other works. Our magnetometry results obtained from large bulk crystals are in very good agreement with the magnetic phase diagram of CrSBr previously predicted by the mean-field theory; A-type antiferromagnetic order is the only phase observed below the Néel temperature at TN = 131 K. Moreover, numerical fits based on the Curie–Weiss law confirm that strong ferromagnetic correlations are present within individual layers even at temperatures much larger than TN.