We explore quantum oscillations in the kagome metals CsTi${}_3$Bi${}_5$ and RbTi${}_3$Bi${}_5$, using high magnetic fields and low temperatures. We reveal new quantum oscillation frequencies in CsTi${}_3$Bi${}_5$, showing a complex Fermi surface that matches density functional theory predictions. Interestingly, the Rb compound exhibits notably different results from the Cs compound, despite theoretical expectations of similarity. This work deepens our understanding of the electronic intricacies within kagome lattice systems and spotlights their role as a playground for unearthing novel quantum states. Our findings pave the way for future investigations in the quantum behaviors of kagome metals, offering insights for advanced material development.

Understanding strongly correlated physics of electronic-driven orbital ordering in transition metal compounds has presented many long-standing questions. Utilizing high-entropy oxides have enabled understanding that disorder can unlock an unusual intermixing of orbital and spin in the rare-earth vanadate, $R$VO${}_3$, which shows that the average and variance of ionic radius determine and control unusual properties of the spin and orbital order. The ability to systematically control variance of the local structure in high-quality crystals which hold constant charge and spin is crucial for a deeper understanding and exploring unanswered decades-old question regarding the physics of the Kugel-Khomskii compounds.

A material with strong in-plane magnetic anisotropy is crucial for determining the magnetization configuration of magnetic materials and their applications in high-density and high-frequency devices. Here, the authors successfully reported a giant interfacial uniaxial in-plane anisotropy in Co/Pt(110) bilayers, which is five times larger than that in Co/Pt(111), the most popular magnetic thin film with perpendicular magnetic anisotropy. Furthermore, such large interfacial magnetic anisotropy can be enhanced by forming a Pt/Co/Pt sandwich structure. These results enabled the integration of in-plane magnetic anisotropy systems into spintronic devices with increased speed and density.

Simultaneous control of noncentrosymmetry and spin-orbit-coupling strength has been demonstrated in a series of chiral molecule-incorporated two-dimensional organic-inorganic hybrid perovskite copper halides (2D-OIHPs) with ferromagnetic exchange interaction. By substituting the halogen from Cl to Br, a systematic change of the magnetic phase diagram from the simple ferromagnetic phase to complicated multiple phases has been observed. This change is due to competition between the ferromagnetic exchange interaction and the Dzyaloshinskii-Moriya interaction. Materials design focusing on the structural flexibility of 2D-OIHP could pave the way to developing new types of nontrivial topological spin systems.

Vanadium dioxide (VO${}_2$) is a promising next-generation electronic material for artificial neural networks. Here, the authors use muon spin spectroscopy to provide a microscopic basis for understanding nanoscale hydrogen diffusion in VO${}_2$, using muons as a microscopic simulator of dilute hydrogen. This innovation allows the authors to investigate the dynamics of trace hydrogen in nanoscale regions such as thin films, which is very difficult to achieve with conventional methods. This study is expected not only to make a significant contribution to the development of VO${}_2$ devices but also to provide a unique method for observing the dynamics of hydrogen at the nanoscale.

This work studied superconductivity and magnetism in infinite-layer nickelate films with scanning SQUID and cross-sectional STEM. The authors found a landscape of superparamagnetism from NiOx nanoparticles that are extrinsic to the superconductivity. They imaged superconducting vortices and determined the penetration depth. They measured the local diamagnetism, finding a consistent value of the penetration depth. The superfluid density exhibits nearly T-linear dependence, suggesting possible $d$-wave superconductivity. Using scanning SQUID to image the various sources of magnetism in superconducting nickelates paves the way for further studies of vortex dynamics and flux quantization in these recently discovered superconductors.

Interlayer van der Waals (vdW) coupling is ubiquitous in two-dimensional materials. The authors explore these interactions in the cuprate (Bi, Pb)${}_2$(Sr,La)${}_2$CuO${}_{6+\delta }$, revealing ultra-low energy phonon modes similar to graphene and transition metal dichalcogenides. Using high-resolution inelastic hard x-ray scattering and first-principles simulations, they reveal vdW phonons from the shear motion of adjacent Bi-O layers. These findings deepen our understanding of the vibrational properties of cuprates and suggest opportunities for the design of novel heterostructures. These results highlight the generic nature of vdW modes in layered materials, including doped copper oxides, and provide insights for future materials design and research.

This research introduces a novel experimental technique to characterize Rydberg excitons in copper oxide (Cu${}_2$O) crystals with sub-micron resolution. By employing spatially resolved resonant absorption spectroscopy and photoluminescence imaging, the study unveils the influence of optically-active charged oxygen vacancies on Rydberg excitons. This approach yields comprehensive spatial maps of exciton properties, including energy, linewidth, and peak absorption without any mobile part, providing valuable insights into crystal quality. The findings highlight the predominant role of charged oxygen vacancies in influencing Rydberg excitons in Cu${}_2$O and offer a reliable method for assessing crystal quality in view of solid-state Rydberg physics.

Spin defects in semiconductors play a major role in quantum technologies. Synthesizing high-quality spin qubits relies on controlling the incorporation of noise sources, such as other, unwanted spin defects, into the host crystal. In this work, the authors provide quantitative calculations of the coherence properties of spin qubits in diamond. They incorporate these results into an existing materials synthesis platform to develop predictive models and $in$ $situ$ feedback for more reliable creation of qubits tailored to applications.

Yttrium iron garnet (YIG) is a prototypical material in the fields of spintronics and magnonics due to its exceptional magnetic properties. However, up to now, the focus has been on planar YIG thin films owing to the challenges associated with manufacturing non-planar structures. Here, the authors demonstrate the fabrication of single crystalline YIG via lateral solid phase epitaxy on top of an artificially defined SiO${}_x$ mesa over micrometer length scales. The reported results lay the foundation for the development of non-planar, epitaxial YIG thin films as well as free standing YIG structures, while still maintaining complete control over the crystal orientation.

Transition metal monosilicides RhSi and CoSi have intriguing physical properties such as long Fermi arc surface states and unusual optical responses. These features originate from multifold fermions - higher spin generalizations of Weyl quasiparticles that are protected by crystalline symmetries. Since these materials are prone to intrinsic disorder, the authors theoretically study topological properties of amorphous RhSi and CoSi. Using the spectral localizer, they find that multifold fermions survive disorder strengths that convert the semimetal into a diffusive metal phase. These conclusions are supported by photoemission simulations showing the presence of Fermi arcs in the corresponding disorder range.

Hydrides at high pressures constitute the only materials to be superconducting above 200 K, and are typically marked by an appreciable hydrogen density of states and van Hove singularities at the Fermi energy. Given the recent interest in nitrogen-doped lutetium hydride, the authors focused on finding the structures which would have electronic properties that could plausibly support high-temperature superconductivity within a narrow pressure range. They have identified a narrow range of stoichiometries Lu${}_8$H${}_{23-x}$N with hydrogen-dominant conduction states, and found one structure which exhibits a very large hydrogen density of states with an extremely sharp van Hove singularity, whose properties may therefore change dramatically under pressure.

Designing conformationally dynamic molecules that self-assemble into predictable nanostructures remains a significant unmet challenge. This work describes the application of atomic-scale cryogenic transmission electron microscopy (cryo-TEM) to elucidate the relationship between molecular structure and self-assembly of block copolymers. Cryo-TEM images revealed the presence of atomic-scale corrugations in sheet-like micelles that are not anticipated by theories which assume that the surfaces of micelles are smooth. The authors propose that the atomic-scale corrugations are due to the dipolar nature of the monomers and interactions between the monomers and water molecules.

Unlocking complex nanostructures like triply periodic minimal surfaces in block copolymer systems poses a crucial hurdle in creating multiscale functional materials. Despite ingenious methods such as interface manipulation, introduction of conformational asymmetry, and chain connectivity regulation, achieving block copolymer self-assembly into nanostructures with high packing frustration remains elusive. In this research update, the authors spotlight the use of end-group chemistry as an effective strategy for stabilizing diverse complex network morphologies beyond the gyroid. Particularly, they redefine phase diagrams by introducing robust end-to-end interactions through end-group and linker chemistry, unveiling unprecedented network structures.