Crystals

We propose a germanium-based temperonic crystal consisting of a two-layer unit cell designed to enable interference of thermal waves in the non-Fourier regime. Each layer features temperature-dependent properties, including thermal diffusivity $D\left(T\right)$, thermal conductivity $\kappa \left(T\right)$, and relaxation time $\tau \left(T\right)$. Utilizing the Cattaneo-Vernotte model, we predict band gaps in the temperature oscillation frequencies. Our analysis reveals that band gaps emerge when one layer is maintained at 110 K and the other at 50 K; however, these gaps close rapidly as the temperature contrast diminishes or the overall temperature increases. Drawing from the temperonic-crystal paradigm and inspired by recent experimental observations of thermal waves in germanium, this design offers a promising pathway for on-chip control of ultrafast thermal pulses and thermal-management devices in semiconductors.

Plastics are essential in modern life but accumulate as waste. Mechanical reprocessing reduces material quality, whereas thermochemical routes require harsh conditions and are costly to upgrade. Together, these factors hinder the large-scale recovery of plastics into equivalent materials. Metal–organic frameworks provide a programmable platform where reticular design fixes porosity and positions well-defined Lewis, Brønsted, redox, and photoredox sites that can preconcentrate oligomers and align scissile bonds for activation. These attributes enable complementary pathways spanning hydrolysis, alcoholysis, aminolysis, photo-oxidation, electrocatalysis, and MOF-derived transformations, with adsorption-guided capture-to-catalysis workflows emerging as integrative schemes. In this review, we establish common figures of merit such as space–time yield, monomer selectivity and purity, energy intensity, site-normalized turnover, and solvent or corrosion footprints. These metrics are connected to design rules that involve active-site chemistry and transport through semi-crystalline substrates. We also emphasize durability under hot aqueous, alcoholic, or oxidative conditions as essential for producing polymer-grade products.

Magnetron sputtering offers a scalable route to magnetic topological insulators (MTIs) based on Cr-doped Sb₂Te₃. We combine a range of X-ray diffraction (XRD), reciprocal-space mapping (RSM), scanning transmission electron microscopy (STEM), scanning TEM-energy-dispersive X-ray spectroscopy (STEM-EDS), and X-ray absorption spectroscopy, and X-ray magnetic circular dichroism (XAS/XMCD) techniques to study the structure and magnetism of Cr-doped Sb₂Te₃ films. Symmetric $\theta$-2$\theta$ XRD and RSM establish a solubility window. Layered tetradymite order persists up to ∼10 at.-% Cr, while higher doping yields CrTe/Cr₂Te₃ secondary phases. STEM reveals nanocrystalline layered stacking at low Cr and loss of long-range layering at higher Cr concentrations, consistent with XRD/RSM. Magnetometry on a 6% film shows soft ferromagnetism at 5 K. XAS and XMCD at the Cr $L_{2,3}$ edges exhibits a depth dependence: total electron yield (TE; surface sensitive) shows both nominal Cr²⁺ and Cr³⁺, whereas fluorescence yield (FY; bulk sensitive) shows a much higher Cr²⁺ weight. Sum rules applied to TEY give $m_L=(0.20\pm 0.04)$${\mu }_{\mathrm{B}}$/Cr, and $m_S=(1.6\pm 0.2)$${\mu }_{\mathrm{B}}$/Cr, whereby we note that the applied maximum field (3 T) likely underestimates $m_S$. These results define a practical growth window and outline key parameters for MTI films.