Despite mounting evidence that materials imperfections are a major obstacle to practical applications of superconducting qubits, connections between microscopic material properties and qubit coherence are poorly understood. Here, we combine measurements of transmon qubit relaxation times (T₁) with spectroscopy and microscopy of the polycrystalline niobium films used in qubit fabrication. By comparing films deposited using three different techniques, we reveal correlations between T₁ and intrinsic film properties such as grain size, enhanced oxygen diffusion along grain boundaries, and the concentration of suboxides near the surface. Qubit and resonator measurements show signatures of two-level system defects, which we propose to be hosted in the grain boundaries and surface oxides. We also show that the residual resistance ratio of the polycrystalline niobium films can be used as a figure of merit for qubit lifetime. This comprehensive approach to understanding qubit decoherence charts a pathway for materials-driven improvements of superconducting qubit performance.

Kagome lattice materials have attracted growing interest for their topological properties and flatbands in electronic structure. We present a comprehensive study on the anisotropy and out-of-plane electric transport in ${\mathrm{Fe}}_3{\mathrm{Sn}}_2$, a metal with bilayer of Fe kagome planes and with massive Dirac fermions that features high-temperature noncollinear magnetic structure and magnetic skyrmions. For the electrical current path along the $c$ axis, in micron-size crystals, we found a large topological Hall effect over a wide temperature range down to spin-glass state. Twofold and fourfold angular magnetoresistance are observed for different magnetic phases, reflecting the competition of magnetic interactions and magnetic anisotropy in kagome lattice that preserve robust topological Hall effect for inter-kagome bilayer currents. This provides new insight into the anisotropy in ${\mathrm{Fe}}_3{\mathrm{Sn}}_2$, of interest in skyrmionic-bubble application-related micron-size devices.

Lightweight microstructures with high area-to-mass ratios, or low surface densities, show great potential applications in microrobots, soft electronics, medical devices, and solar sailing. However, the bending stiffness of such microstructures is usually too low to work effectively. In order to obtain active microstructures with enhanced bending stiffness, a new design for thermally actuated multilayered metallic microstructures with high area-to-mass ratios is presented in this article. The microstructures made of aluminum and NiTi alloy are fabricated to demonstrate the feasibility of vertical deployment of such microstructures under thermal actuation. The concept design and working principle of designed multilayered metallic microstructures are based on symmetrical deposition of metals Al\NiTi\NiTi\Al, followed by practical microfabrication processes, such as photolithography, physical vapor deposition (PVD), and dry etch. The area-to-mass ratios of such microstructures could be up to 400 m2/kg. Then, experiments for electrical characterization are set up for thermal actuation or Joule heating. Besides that, the equivalent resistances of such microstructures with regard to temperatures are calibrated, allowing for the determination of in situ temperatures of deformed microstructures when being heated in the vacuum chamber of scanning electron microscope (SEM). Finally, vertical deployment of such thin microstructures is detected and measured, which validates the feasibility of stiffness enhancement through the symmetrical design and thermal actuation.

Separation membranes are critical for a range of processes, including but not limited to water desalination, chemical and fuel production, and recycling and recovery applications. Fundamentally, there are intrinsic trade-offs between permeability and selectivity. Local water organization and content can impact membrane structure (short- and long-range) in laminar transition metal carbide (MXene) membranes and impact selective ion permeation. Intercalation of chaotropic cesium (Cs + ) ions within the layers reduces the water content in the membrane and at the surface which cannot be found in the intercalation of other ions. Additionally, 3D imaging using focused ion beam scanning electron microscopy showed fewer defects in the Cs-MXene membrane, due to reduced local water content, leading to more efficient ion sieving. X-ray diffraction and density functional theory calculations on the nanochannel structure demonstrated that the chaotropic ion results in the smallest nanochannel size and induces a stronger resistance to water-induced nanochannel swelling. With a narrower nanochannel, the Cs-MXene membrane limits ion transport pathways, resulting in more selective transport of lithium over other metal cations, as evidenced in both experiment and molecular dynamics simulations. Our findings highlight the potential for controlling the structural organization of 2D MXene membranes to enable on-demand transport of ions for diverse applications.