Pressure-induced superconducting phases and electronic reconstruction in layered RbMgBi

Abstract

<p>We report the discovery of pressure-induced superconductivity transitions in RbMgBi, a nonmetallic layered compound under ambient conditions. Upon compression, RbMgBi first undergoes an insulator-to-metal transition at ∼4.5GPa, coinciding with the emergence of a superconducting phase (SC-I). A second superconducting phase (SC-II) appears near 10.4 GPa, with both phases coexisting until SC-II becomes dominant above ∼14GPa. High-pressure ac susceptibility confirmed the bulk superconducting nature in both phases. High-pressure x-ray diffraction reveals a substantial 𝑐-axis contraction and a structural transition from a tetragonal 𝑃⁢4/<em>nmm</em> to an orthorhombic <em>Cmcm</em> phase near 5.5 GPa, underscoring the role of interlayer spacing in enabling superconductivity. Hall measurements show marked carrier evolution at the critical pressures, while first-principles calculations indicate a pressure-driven electronic reconstruction—from a single-band regime to a multiband state with enhanced Fermi velocity and superfluid density. Our results demonstrate a strong interplay between structural compression, carrier dynamics, and superconducting behavior, offering new insight into pressure-tuned superconductivity and guiding principles for designing emergent superconductors via coupled structural-electronic engineering.<br></p>