Grain Boundaries Induced a Class of Carbon Allotropes with Dirac Fermions

Abstract

The incorporation of a nonbenzenoid network into graphene grain boundary is an effectual approach for mechanical properties, thermal transport, and band engineering. Here, we propose that different kinds of Dirac semimetals can be induced by grain boundaries (GBs) in graphene. Our results show that the electronic properties can be periodically oscillated between metal and semimetal, and even from type-II nodal point semimetal (NPS) to type-I NPS, all determined only by the spacing of the GBs. Additionally, the topological properties are confirmed by nonzero Berry curvature and topologically protected surface state. Our findings offer an attractive approach for designing carbon-based topological devices.

Stability of 2D Crystals from Tessellation

“…Among the proposed 2D carbons in previous studies, the dominant structures are constructed by pure sp 2 carbon atoms, usually forming networks of square, pentagon, hexagon, heptagon, and octagon rings. [ 5 ] These 2D sp 2 carbon networks have been found to be semiconducting, metallic or semi‐metallic with Dirac cones. [ 6 ] Besides, 2D graphyne (‐like) structures, which consist of sp and sp 2 carbon atoms, [ 7 ] were proposed and γ‐graphyne was successfully synthesized very recently.…”

A carbon allotrope with twisted Dirac cones induced by grain boundaries composed of pentagons and octagons

“…Another highly sought-after object is the topologically nontrivial electronic properties. Graphene-like topological semimetallic materials have been expanded in recent theoretical studies, [33][34][35][36] and a small number of them have even been prepared experimentally. Biphenylene, 37 whose GBs consist of eight-and four-membered rings, was prepared recently, 38 and phagraphene 39 containing seven-and five-membered rings was achieved through on-surface synthesis.…”

From Topological Nodal-Line Semimetal to Insulator in ABW-Ge4: A New Member of the Germanium Allotrope

“…Owing to the complex potential energy surface, the Group-IV elements can form various allotropes with different structural and electronic properties, which provides promising platforms for constructing multifunctional microelectronic devices. Hence, the searching for stable Group-IV allotropes has attracted considerable attention from both theoretical and experimental researchers. − However, these studies mainly focus on carbon (C) and silicon (Si), and the studies about germanium (Ge) allotropes are relatively few. The most prominent Ge allotrope is the diamond-cubic Ge, denoted as dc-Ge, which has higher electron and hole mobilities, and smaller indirect band gap with respect to that of dc-Si .…”

“…Hence, the searching for stable Group-IV allotropes has attracted considerable attention from both theoretical and experimental researchers. 2 − 5 However, these studies mainly focus on carbon (C) and silicon (Si), and the studies about germanium (Ge) allotropes are relatively few. The most prominent Ge allotrope is the diamond-cubic Ge, denoted as dc-Ge, which has higher electron and hole mobilities, and smaller indirect band gap with respect to that of dc-Si.…”