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Abstract Cuprate high-temperature superconductors (HTSCs) have long stood a promising candidates for various applications due to their high critical temperature ( $T_{\mathrm{c}}$ ) at ambient pressure. Practical limitations such as low bulk critical current densities ( $J_{\mathrm{c}}^{\mathrm{B}}$ ), sample inhomogeneities and chemical instability, however, have hindered their applicability. Increasing ${\mathit{T}}_{\mathrm{c}}$ , $J_{\mathrm{c}}^{\mathrm{B}}$ and the upper critical fields as well as maintaining the chemical stability in cuprates are therefore major goals for these materials science. Here, we characterize the electronic and structural properties of an Ag intercalated ${\mathrm{Bi}}_{1.6}{\mathrm{Pb}}_{0.4}{\mathrm{Sr}}_2{\mathrm{Ca}}_2{\mathrm{Cu}}_3{\mathrm{O}}_{10+\delta }$ sample prepared using a novel growth technique. The sample demonstrates enhanced electrical properties that have remained nearly constant over 8 years, while the non-silver Bi-2223 exhibits much degradation in both high- $T_{\mathrm{c}}$ fractional phase and superconducting properties. We correlate these bulk electronic properties with structural probes to determine the critical role of Ag in these samples. The enhanced properties of these Ag intercalated cuprates suggest novel synthesis pathways will be key in developing more practical superconductors for applications. 

The search for high-temperature superconductivity among pressure-stabilized hydrides has received great interest since theory-directed clathrate hydrides, such as CaH6, YH6, YH9, and LaH10, were synthesized and shown to exhibit a superconducting critical temperature (Tc) above 200 K. However, further tuning the superconductivity and stability of these prominent hydrides to enhance their applicability remains a significant challenge. Here, we take the sodalite-like clathrate prototype MH6 (M = Ca, Y, etc.) as an example to investigate the stability and superconductivity of multicomponent metal hydrides containing four different metal atoms for each structure. High-throughput simulations of 1820 ABCDH24 quinary hydrides with initial symmetry of F4" 3m, where A, B, C, and D represent different metal atoms were performed. The calculations reveal 119 structures that are dynamically stable at 300 GPa and 67 structures exhibit superconductivity exceeding 200 K, and 20 are found to have Tcs above 260 K. Notable among these quinary alloy hydrides, (Na,Zr,Mg,Hf)H6 is predicted to have a Tc approaching room temperature at 250 GPa. Both configurational and vibrational entropy play important roles in stabilizing these alloy structures. (Na,Y,Zr,Hf)H6, (Mg,Zr,Sc,Y)H6, and (Mg,Hf,Ca,Zr)H6 were computed to be thermodynamically stable, making them promising candidates for experimental synthesis. These quinary superconducting hydrides may facilitate realization of very high-temperature superconductors that are stable over a broader range of conditions than those found for binary or ternary systems. 

Experimental constraints and sample limitations can preclude ideal measurements of electrical transport properties of materials. In such situations, AC electrical transport methods are often employed due to a significant increase in signal-to-noise ratio they can provide. However, dynamic effects that are not often accounted for may be present that may modify the signals in these measurements. In particular, dynamic filtering effects are prominent in small, granular, and heterogeneous materials. We demonstrate that a lock-in amplifier based circuit can distinguish between these DC transport and AC filtering effects. We further demonstrate that this filtering can reveal distinct signatures of magnetic transitions while providing a measure of sample quality. 

While hydrogen-rich materials have been demonstrated to exhibit high T_csuperconductivity at high pressures, there is an ongoing search for ternary, quaternary, and more chemically complex hydrides that achieve such high critical temperatures at much lower pressures. First-principles searches are impeded by the computational complexity of solving the Eliashberg equations for large, complex crystal structures. Here, we adopt a simplified approach using electronic indicators previously established to be correlated with superconductivity in hydrides. This is used to study complex hydride structures, which are predicted to exhibit promisingly high critical temperatures for superconductivity. In particular, we propose three classes of hydrides inspired by the Fm $\overline{3}$ m RH ${}_3$ structures that exhibit strong hydrogen network connectivity, as defined through the electron localization function. The first class [RH ${}_{11}$ X ${}_3$ Y] is based on a Pm $\overline{3}$ m structure showing moderately high T_c, where the T_cestimate from electronic properties is compared with direct Eliashberg calculations and found to be surprisingly accurate. The second class of structures [(RH ${}_{11}$ ) ${}_2$ X ${}_6$ YZ] improves on this with promisingly high density of states with dominant hydrogen character at the Fermi energy, typically enhancing T_c. The third class [(R ${}^1$ H ${}_{11}$ )(R ${}^2$ H ${}_{11}$ )X ${}_6$ YZ] improves the strong hydrogen network connectivity by introducing anisotropy in the hydrogen network through a specific doping pattern. These design principles and associated model structures provide flexibility to optimize both T_cand the structural stability of complex hydrides. 

Abstract Understanding how microscopic structural domains govern macroscopic electronic properties is central to advancing hydride superconductors, yet such correlations remain poorly resolved under pressure. We report the synthesis and characterization of (La_0.9Y_0.1)H₁₀superhydrides exhibiting coexisting cubic$${Fm}\bar{3}m$$ $Fm\overline{3}m$ and hexagonal$$P{6}_{3}/{mmc}$$ $P{6}_3/mmc$ clathrate phases observed over the pressure range from 168 GPa down to 136 GPa. Using synchrotron-based X-ray diffraction imaging at the upgraded Advanced Photon Source, we spatially resolved μm-scale distributions of these phases, revealing structural inhomogeneity across the sample. Four-probe resistance measurements confirmed superconductivity with two distinct transitions: an onset at 244 K associated with the cubic phase and a second near 220 K linked to the hexagonal phase. Notably, resistance profiles collected from multiple current and voltage permutations showed variations in transition width and onset temperature that correlated with the spatial phase distribution. These findings demonstrate a direct connection between local structural domains and superconducting behavior. 

We demonstrate a remarkable change in the chemical bonding of iron under pressure that underlies the distribution of elements in the Earth’s mantle and core. Using a massive-scale, first-principles study, we show that while reacting withp-block elements under increasing pressure from ambient to Earth core conditions, iron tends to reverse its redox nature, changing from an electron donor (reductant) to an electron acceptor (oxidant), and oxidizes manyp-block elements. Such reverse redox propensity significantly impacts the stoichiometries, bond types and strengths, structures, and properties of iron compounds under deep planetary conditions. This change transforms manyp-block elements (conventionally labeled lithophile or chalcophile) into highly siderophile species. The chemical binding strengths with iron show an inverse correlation with the depletion ofp-block elements in the silicate Earth. Furthermore, silicon shows a distinct anomaly in its bonding to iron, which suggests silicon may readily be incorporated into Earth’s core. 

The abrupt drop of resistance to zero at a critical temperature is a key signature of the current paradigm of the metal–superconductor transition. However, the emergence of an intermediate bosonic insulating state characterized by a resistance peak preceding the onset of the superconducting transition has challenged this traditional understanding. Notably, this phenomenon has been predominantly observed in disordered or chemically doped low-dimensional systems, raising intriguing questions about the generality of the effect and its underlying fundamental physics. Here, we present a systematic experimental study of compressed elemental sulfur, an undoped three-dimensional (3D) high-pressure superconductor, with detailed measurements of electrical resistance as a function of temperature, magnetic field, and current. The anomalous resistance peak observed in this 3D system is interpreted based on an empirical model of a metal–bosonic insulator–superconductor transition, potentially driven by vortex dynamics under magnetic field and energy dissipation processes. These findings offer a fresh platform for theoretical analysis of the decades-long enigmatic of the underlying mechanism of this phenomenon.