Electronic structure, magnetism, and high-temperature superconductivity in multilayer octagraphene and octagraphite

Abstract

We systematically investigate the electronic structure, magnetism, and high-temperature superconductivity (SC) in multilayer octagraphene and octagraphite (bulk octagraphene). A tight-binding model is used to fit the electronic structures of single-layer and multilayer octagraphenes and octagraphite. We find that multilayer octagraphene and octagraphite follow a simple A-A stacking structure from the energy analysis. The van der Waals interaction induces ${t}_{\ensuremath{\perp}}\ensuremath{\approx}0.25$ eV and the hopping integral within each layer changes little when the layer number $n$ increases. There is a well Fermi-surface nesting with nesting vector $\mathbf{Q}=(\ensuremath{\pi},\ensuremath{\pi})$ for single-layer octagraphene at half-filling, which can induce a two-dimensional N\'eel antiferromagnetic order. With increasing layer number $n\ensuremath{\rightarrow}\ensuremath{\infty}$, the Fermi-surface nesting transforms to three-dimensional (3D) with nesting vector $\mathbf{Q}=(\ensuremath{\pi},\ensuremath{\pi},\ensuremath{\pi})$ and shows that the system has a 3D N\'eel antiferromagnetic order. Upon doping, multilayer octagraphene and octagraphite can enter a high-temperature ${s}^{\ifmmode\pm\else\textpm\fi{}}$ SC driven by spin fluctuation. We evaluate the superconducting transition temperature ${T}_{c}$ by using the random-phase approximation, which yields a high ${T}_{c}$ even if the layer number $n\ensuremath{\ge}3$. Our study shows that multilayer octagraphene and octagraphite are promising candidates for realizing high-temperature SC.