Synthesis of medium-entropy alloy superhydride <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML"> <mml:mrow> <mml:mrow> <mml:mo>(</mml:mo> <mml:mi>La</mml:mi> <mml:mo>,</mml:mo> <mml:mi mathvariant="normal">Y</mml:mi> <mml:mo>,</mml:mo> <mml:mi>Ce</mml:mi> <mml:mo>)</mml:mo> </mml:mrow> <mml:msub> <mml:mi mathvariant="normal">H</mml:mi> <mml:mrow> <mml:mn>10</mml:mn> <mml:mo>±</mml:mo> <mml:mi>x</mml:mi> </mml:mrow> </mml:msub> </mml:mrow> </mml:math> with high-temperature superconductivity under high pressure
Chuanheng Ma, Mi Zhou, Jingkai Bi, Yuan Ma, Dongdong Li, Hanyu Liu, Guangtao Liu, Hongbo Wang, Yanming Ma
Abstract
Metal substitutions have been recognized as an efficient approach for exploring unusual superhydrides, aiming to discover configurations with diverse structures and enhanced superconductivity. However, the roles of the metal type and concentration on high-temperature superconducting (high-${T}_{\mathrm{c}}$) hydrides with multiple components remain underexplored in this rapidly advancing domain. In this study, we conducted extensive experiments on the equimolar La-Ce-Y alloy superhydride with the highest configuration entropy among quaternary hydrides under pressure. In situ X-ray diffraction measurements revealed the synthesis of a hexagonal close-packed (hcp) $P{6}_{3}$/mmc-$(\mathrm{La},\mathrm{Ce},\mathrm{Y}){{\mathrm{H}}_{10}}_{\ifmmode\pm\else\textpm\fi{}x}$ ($\ensuremath{-}0.2<x<+0.4$), which could be stable down to the lowest pressure of 96 GPa. Notably, despite numerous efforts, such an unprecedented hcp decahydride subunit has remained unattainable in corresponding binary hydrides, highlighting the powerful influence of the entropy effect on stability and hydrogen concentration in this multicomponent system. Further electrical transport measurements confirmed its superconductivity, as evidenced by zero resistance and suppression of superconductivity under applied magnetic fields, with a maximum ${T}_{\mathrm{c}}$ of 165 K. These findings serve as a paradigmatic example, investigating entropy effects in multinary systems and opening up the exciting potential for further exploration of high-${T}_{\mathrm{c}}$ alloy superhydrides.