The annual report also presents our recent technical development as well as facts and figures about MGML, our user program and our involvement in international structures.

The initial setup has been continuously optimized, balancing several key parameters—such as accessible sample space diameter versus beam size—to improve the quality of the collected data. The highest pressures reached so far are 23 GPa (UCu₂P₂) and 30 GPa (EuRu₂P₂), with further improvements likely possible through continued optimization and natural ageing of the pressure cell.

These developments have already contributed to multiple student projects, including a Ph.D. thesis (P. Král, 2024), a Bc. thesis (M. Jesenič, 2024), and a student faculty grant (M. Bystrický). Data from these initial experiments have been published or are currently being prepared for publication.

Despite being performed in a laboratory setting rather than at a synchrotron, the data quality is sufficient to observe the pressure dependence of lattice constants, detect pressure-induced structural transitions, and identify signs of pressure-induced valence transitions. These results have already supported successful beamtime proposals at international high-pressure facilities.

The annual report also presents our recent technical development as well as facts and figures about MGML, our user program and our involvement in international structures.

The research focuses on the unconventional superconductor UTe₂, a promising candidate for spin-triplet pairing. Using pulsed magnetic fields up to 70 Tesla, researchers observed that the superconducting critical temperature (T_c) increases to approximately 2.4 K under magnetic fields near 40 Tesla. This finding is counterintuitive, as magnetic fields typically suppress superconductivity; however, in this case, they appear to stabilize and enhance it under specific conditions.

While these extreme conditions are far from practical for technological applications, this work provides critical insights into the unique mechanisms driving superconductivity in UTe₂ and related materials. By advancing our understanding of the interplay between magnetism and superconductivity, this study contributes to the broader effort to unravel the physics of unconventional superconductors.

The high-quality single crystals of UTe₂ used in this study were prepared by Dr. M. Vališka’s team at MGML. For more details, see our previous posts tagged UTe₂.

This large-scale collaboration was made possible through dual access provided by the ISABEL project.

The findings reveal that the dynamics of this frustrated antipolar phase are governed by a thermally activated process, exhibiting a slowdown as the system cools, ultimately leading to a complete freezing at zero temperature. This behavior provides a deeper understanding of frustration in electric dipole systems and opens avenues for further research into analogous phenomena in other materials.

A recent paper published in Proceedings of the National Academy of Sciences reveals a significantly revised high magnetic field superconducting phase diagram in the ultraclean limit of single crystals. The study demonstrates a pronounced sensitivity of field-induced superconductivity to the presence of crystalline disorder. A theoretical model developed to describe the experimental results shows how critical magnetic fluctuations in high magnetic fields may drive a transition between two distinct spin-triplet superconducting phases in UTe₂.

The high quality single crystals of UTe₂ for this study were prepared by Dr. M. Vališka’s team at MGML using the molten salt flux (MSF) technique. The team used high-purity uranium metal, further refined through the solid-state electrotransport technique available in the MGML infrastructure. The pristine quality of the resulting single crystals is evidenced by their high critical temperature (T_c) values of up to 2.10 K, low residual resistivity down to 0.48 µΩ·cm, and the observation of magnetic quantum oscillations.

This large-scale collaboration benefited from dual access via the ISABEL project.

Thanks to funding received from the Research Infrastructures I call under the Jan Amos Komenský Operational Programme (project number: CZ.02.01.01/00/23_015/0008184), MGML will be able to renew its existing equipment and strategically develop its experimental facilities during the 2024–2026 period. This investment will enable the lab to stay at the forefront of scientific research and meet the growing demands of its user community.

The project includes the necessary expansion of frequency ranges for measuring alternating electrical and magnetic properties as well as multiferroic phenomena. Several diffractometers for detailed structural characterization will be updated, and the lab’s capabilities for pressure measurements will be significantly enhanced. Furthermore, a new X-ray fluorescence spectrometer will be acquired for precise chemical analysis of prepared samples.

Stay tuned for updates on the advancements and new capabilities at MGML in the coming years!

In this paper, the authors confirm the presence of lifted Kramers spin degeneracy (LKSD) without net magnetization or inversion-symmetry breaking using photoemission spectroscopy and ab initio calculations. They identify two distinct, unconventional mechanisms of LKSD induced by the altermagnetic phase of centrosymmetric MnTe, which has no net magnetization. The study reveals that altermagnetic LKSD could significantly impact magnetism, motivating further exploration and exploitation of this unconventional magnetic phase across a broad range of materials, including insulators, semiconductors, metals, and superconductors.