Structural Stability, Electronic Band Structure, and Spin–Orbit Coupling Effects in Two–Dimensional Stanene

This study investigates the structural and electronic properties of monolayer stanene, a two-dimensional honeycomb material composed of tin atoms. The calculations were performed within the framework of density functional theory as implemented in the Quantum ESPRESSO package. We systematically examined the total energy convergence, lattice constant relaxation, and k-point sampling to ensure reliable predictions. The optimized geometry reveals a low-buckled honeycomb structure rather than a perfectly planar one, which is found to be energetically more stable. The calculated lattice constant, bond length, and buckling height are in good agreement with previously reported theoretical and experimental values. The electronic band structure without spin-orbit coupling shows linear dispersion near the high symmetry K and K′ points, similar to graphene, indicating that charge carriers behave as massless Dirac fermions. In this case, stanene exhibits a gapless semimetallic character. However, when spin-orbit coupling is included, a direct band gap opens at the Dirac point, transforming stanene into a topological insulator with potential for dissipationless electronic transport. The total and partial density of states further confirm the semimetallic nature and highlight the dominant contribution of pz orbitals near the Fermi level. The mixed sp²–sp³ hybridization due to buckling is responsible for the deviation from ideal planar symmetry. Our computed results align well with existing literature, validating the accuracy of our computational approach. Overall, this work provides a clear understanding of how structural buckling and spin-orbit coupling together govern the electronic behavior of stanene, making it a promising candidate for future nanoelectronic and spintronic devices.