Dirac Band Evolution in Orthorhombic Au ₂ Pb Due to External Pressure and Spin–Orbit Couplings for Applications in Topological Quantum and Spintronic Devices

Gold–lead intermetallic Au 2 Pb has emerged as a promising platform for exploring the interplay between relativistic effects, Dirac physics, and superconductivity. Inspired from the previous work [ Phys. Rev. B 2018, 98, 161107], here, we present a systematic first-principles investigation of the orthorhombic, nonmagnetic Pbcn phase of Au 2 Pb, focusing on the combined roles of spin–orbit coupling (SOC) and external pressure on its electronic structure. In the absence of SOC, Dirac-like band crossings appear along high-symmetry directions; inclusion of SOC lifts band degeneracies and strongly reshapes these crossings. Fully relativistic and nonrelativistic density functional theory calculations reveal that the low-energy states near the Fermi level are dominated by Au-d and Pb-p orbitals, while Pb-d contributions are negligible. Our pressure-dependent analysis (0–40 GPa) shows that moderate compression (10–20 GPa) stabilizes Dirac cones close to the Fermi level, whereas higher pressure drives a clear SOC-induced opening of the Dirac cone, signaling a pressure-driven topological phase transition. The evolution of the density of states and band dispersions indicates enhanced orbital hybridization and bandwidth under pressure, leading to tunable relativistic band splitting and gap formation. These findings provide a microscopic mechanism for controlling topological electronic states in Au 2 Pb and establish pressure as an effective tuning parameter for engineering Dirac physics and potential topological superconductivity. The present results offer direct relevance to ongoing high-pressure experiments and position Au 2 Pb as a versatile quantum material for topological and superconducting applications.