Pressure-Induced Structural-Electronic Coevolution and Tunable Superconductivity in Bismuth
Group-VA elements readily undergo intricate structural reconstruction and electronic-state evolution under high pressure, exhibiting abundant phase-transition behaviours and exotic superconducting properties, which makes them ideal model systems for investigating the microscopic mechanisms of high-pressure superconductivity. Bismuth undergoes successive structural phase transitions upon compression. Nevertheless, systematic studies on the electron-phonon coupling and superconducting behaviour of its final stable body-centered-cubic Bi-V phase are still lacking. In this work, first-principles density-functional theory and density-functional perturbation theory are adopted to explore the coupled structural-electronic evolution and tunable superconductivity of Bi-V across the range from metastable to high-pressure stable states. Electronic-structure results demonstrate that compression enhances the degree of electron delocalization of the system. In the Bi-IV phase, the Bi-p and Bi-d orbitals contribute comparably to the density of states at the Fermi level. Further investigations on bcc Bi-V reveal that the system at the 15 GPa phase-transition boundary possesses a high Fermi-level density of states and a large logarithmic-mean phonon frequency, corresponding to a superconducting critical temperature (T c =5.58 K). By contrast, prominent phonon softening under the metastable condition of 10 GPa substantially strengthens electron-phonon coupling and yields a higher superconducting transition temperature. By comparing the superconducting behaviours of Bi-V at 10 GPa, 15 GPa and higher pressures, this work reveals the physical picture of superconductivity modulated by metastability-driven phonon softening. These findings clarify the intrinsic correlation among structural evolution, electronic states and superconductivity in high-pressure bismuth, deepen the understanding of high-pressure superconducting mechanisms in group VA-element systems, and provide theoretical references for exploring the mechanisms of high-pressure superconductivity.