X-ray-diffraction and electrical-transport imaging of superconducting superhydride (La,Y)H10

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)H₁₀ superhydrides exhibiting coexisting cubic <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML"><mml:mi>F</mml:mi> <mml:mi>m</mml:mi> <mml:mover><mml:mrow><mml:mn>3</mml:mn></mml:mrow> <mml:mo>¯</mml:mo></mml:mover> <mml:mi>m</mml:mi></mml:math> and hexagonal <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML"><mml:mi>P</mml:mi> <mml:msub><mml:mrow><mml:mn>6</mml:mn></mml:mrow> <mml:mrow><mml:mn>3</mml:mn></mml:mrow> </mml:msub> <mml:mo>/</mml:mo> <mml:mi>m</mml:mi> <mml:mi>m</mml:mi> <mml:mi>c</mml:mi></mml:math> 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.