No abstract

The recent observation of room-temperature superconductivity will undoubtedly lead to a surge in the discovery of new, dense, hydrogen-rich materials. The rare earth metal superhydrides are predicted to have very high-Tc superconductivity that is tunable with changes in stoichiometry or doping. Here we report the synthesis of a yttrium superhydride that exhibits superconductivity at a critical temperature of 262 K at 182 ± 8 GPa. A palladium thin film assists the synthesis by protecting the sputtered yttrium from oxidation and promoting subsequent hydrogenation. Phononmediated superconductivity is established by the observation of zero resistance, an isotope effect and the reduction of Tc under an external magnetic field. The upper critical magnetic field is 103 T at zero temperature.

No abstract

The competing and non‐equilibrium phase transitions, involving dynamic tunability of cooperative electronic and magnetic states in strongly correlated materials, show great promise in quantum sensing and information technology. To date, the stabilization of transient states is still in the preliminary stage, particularly with respect to molecular electronic solids. Here, a dynamic and cooperative phase in potassium‐7,7,8,8‐tetracyanoquinodimethane (K‐TCNQ) with the control of pulsed electromagnetic excitation is demonstrated. Simultaneous dynamic and coherent lattice perturbation with 8 ns pulsed laser (532 nm, 15 MW cm−2, 10 Hz) in such a molecular electronic crystal initiates a stable long‐lived (over 400 days) conducting paramagnetic state (≈42 Ωcm), showing the charge–spin bistability over a broad temperature range from 2 to 360 K. Comprehensive noise spectroscopy, in situ high‐pressure measurements, electron spin resonance (ESR), theoretical model, and scanning tunneling microscopy/spectroscopy (STM/STS) studies provide further evidence that such a transition is cooperative, requiring a dedicated charge–spin–lattice decoupling to activate and subsequently stabilize nonequilibrium phase. The cooperativity triggered by ultrahigh‐strain‐rate (above 106 s−1) pulsed excitation offers a collective control toward the generation and stabilization of strongly correlated electronic and magnetic orders in molecular electronic solids and offers unique electro‐magnetic phases with technological promises.

No abstract