Robust band gap and half-metallicity in graphene with triangular perforations

TL;DR

This study demonstrates that triangular perforations in graphene create robust band gaps and half-metallicity, even with disorder, offering promising avenues for spintronic applications.

Contribution

It introduces a new approach using triangular antidots with zigzag edges to achieve robust band gaps and half-metallicity in graphene, resilient to disorder.

Findings

Large band gaps from zigzag-edged antidots are robust against disorder.

Spin polarization induces significant magnetic moments and half-metallicity.

Half-metallic behavior persists under realistic disorder conditions.

Abstract

Ideal graphene antidot lattices are predicted to show promising band gap behavior (i.e., $E_G\simeq 500$ meV) under carefully specified conditions. However, for the structures studied so far this behavior is critically dependent on superlattice geometry and is not robust against experimentally realistic disorders. Here we study a rectangular array of triangular antidots with zigzag edge geometries and show that their band gap behavior qualitatively differs from the standard behavior which is exhibited, e.g, by rectangular arrays of armchair-edged triangles. In the spin unpolarized case, zigzag-edged antidots give rise to large band gaps compared to armchair-edged antidots, irrespective of the rules which govern the existence of gaps in armchair-edged antidot lattices. In addition the zigzag-edged antidots appear more robust than armchair-edged antidots in the presence of geometrical disorder. The inclusion of spin polarization within a mean-field Hubbard approach gives rise to a large overall magnetic moment at each antidot due to the sublattice imbalance imposed by the triangular geometry. Half-metallic behavior arises from the formation of spin-split dispersive states near the Fermi energy, reducing the band gaps compared to the unpolarized case. This behavior is also found to be robust in the presence of disorder. Our results highlight the possibilities of using triangular perforations in graphene to open electronic band gaps in systems with experimentally realistic levels of disorder, and furthermore, of exploiting the strong spin dependence of the system for spintronic applications.