Potential enhancement of superconductivity in MgB2 nanosheets: First-principles calculations

First-principles calculations based on density functional theory are performed on the three types of free-standing MgB2 (0 0 0 1) nanosheets with different thickness and surface terminations. The results show that the surface electronic-states and electron-localization behaviors are mainly tuned by surface terminations. The higher Mg compositions at the surface facilitate the covalent bonding of B honeycomb, and give rise to the stronger surface electronic-states and more localized electrons at the surface. The most remarkable feature is that the thinner nanosheets generally exhibit the higher density of states at Fermi energy level, suggesting the potential increase in the superconducting critical temperature.