Correlated Magnetic States in Extended One-Dimensional Defects in Graphene

Abstract

Ab initio calculations indicate that while the electronic states introduced by tilt grain boundaries in graphene are only partially confined to the defect core, a translational grain boundary introduces states near the Fermi level that are very strongly confined to the core of the defect, and display a ferromagnetic instability. The translational boundary lies along a graphene zigzag direction and its magnetic state is akin to that which has been theoretically predicted to occur on zigzag edges of graphene ribbons. Unlike ribbon edges, the translational grain boundary is fully immersed within the bulk of graphene, hence its magnetic state is protected from the contamination and reconstruction effects that have hampered experimental detection of the magnetic ribbon states. Moreover, our calculations suggest that charge transfer between grain boundaries and the bulk in graphene is short ranged, with charge redistribution confined to ~5 Å from the geometric center of the 1D defects.

Grain boundaries with octagonal defects in graphene nanoribbons and nanotubes

“…This is because they present localized states at the Fermi level, which influence their transport and magnetic properties. [7][8][9][10][11] Grain boundaries in graphene can be seen as defect lines formed at junctions between sheets of graphene or graphene ribbons. Experimental techniques nowadays allow the patterning of graphene into nanometer-size ribbons with well-controlled size and shape of the edges.…”

Topologically Protected Metallic States Induced by a One-Dimensional Extended Defect in the Bulk of a 2D Topological Insulator

“…The 1D extended defect in our study is a buckled version of the so-called 558-defect, composed of periodic units consisting of one octogonal and two pentagonal rings, as shown in Fig.1(c). A flat version of the 558-defect has been shown experimentally to occur in graphene monolayers [10,11], and theoretically to display magnetic quasi-1D electronic states in n-doped layers [12,13].…”

Electron interaction, charging, and screening at grain boundaries in graphene

“…It has been shown before that the (2,0) GB in neutral graphene is spin polarized with the ferromagnetic ground state. 16,17,21,22 Our calculations based on the Hamiltonian Eq. (3) show that this state remains fully spin-polarized in electrostatically doped graphene at a finite V g with the electron population being completely dominated by species of the same spin; see Fig.…”

“…The first one, (2,0), consists of domains with the aligned crystallographic orientations θ L = θ R = θ = 0 • (d ≈ 0.5 nm) and separated by a zigzag-oriented interface of one octagon and two side-sharing pentagons. [16][17][18][19]23 The repeat vector (2,1) of the second one implies θ L = θ R = θ = 10.9 • (d ≈ 0.65 nm) and its interface region includes pentagon-heptagon pairs. 6,17 We would like to note that while we study two representative GBs, (2,0) and (2,1) (corresponding to aligned and misaligned crystallographic orientations), we believe that our findings are generic and remain valid for other GBs in graphene.…”

“…[12][13][14][15] This provides a strong motivation for investigation of morphological, electronic, and spin properties of GBs. A number of studies have been recently reported addressing the band structure, [16][17][18][19][20] spin polarization, 16,17,21,22 electron transport and scattering 12,13,20 in GBs. However, all these studies were limited to the case of electrically neutral graphene, and very little is presently known on how the electronic and transport properties of GBs are modified at nonzero electron densities (i.e., away from the Dirac point).…”