title: Configuration of ripple domains and their topological defects formed under local mechanical stress on hexagonal monolayer graphene.
abstract: Ripples in graphene are extensively investigated because they ensure the mechanical stability of two-dimensional graphene and affect its electronic properties. They arise from spontaneous symmetry breaking and are usually manifested in the form of domains with long-range order. It is expected that topological defects accompany a material exhibiting long-range order, whose functionality depends on characteristics of domains and topological defects. However, there remains a lack of understanding regarding ripple domains and their topological defects formed on monolayer graphene. Here we explore configuration of ripple domains and their topological defects in exfoliated monolayer graphenes on SiO2/Si substrates using transverse shear microscope. We observe three-color domains with three different ripple directions, which meet at a core. Furthermore, the closed domain is surrounded by an even number of cores connected together by domain boundaries, similar to topological vortex and anti-vortex pairs. In addition, we have found that axisymmetric three-color domains can be induced around nanoparticles underneath the graphene. This fascinating configuration of ripple domains may result from the intrinsic hexagonal symmetry of two-dimensional graphene, which is supported by theoretical simulation using molecular dynamics. Our findings are expected to play a key role in understanding of ripple physics in graphene and other two-dimensional materials.
authors: Division of Quantum Phases &devices, Department of Physics, Konkuk University, Seoul, 143-701, Korea.
authors: Yeonggu
authors: Y
authors: Park
authors: Creative Research Center for Graphene Electronics, Electronics and Telecommunications Research Institute (ETRI), Daejeon 305-700, Korea.
authors: Jin Sik
authors: JS
authors: Choi
authors: Hybrid Materials Research Center, Department of Nanotechnology and Advanced Materials Engineering, Sejong University, Seoul 143-747, Korea.
authors: Taekjib
authors: T
authors: Choi
authors: Division of Quantum Phases &devices, Department of Physics, Konkuk University, Seoul, 143-701, Korea.
authors: Mi Jung
authors: MJ
authors: Lee
authors: 1] Division of Quantum Phases &devices, Department of Physics, Konkuk University, Seoul, 143-701, Korea [2] Center for Integrated Nanotechnologies (CINT), Los Alamos National Laboratory, Los Alamos, New Mexico 87545, USA.
authors: Quanxi
authors: Q
authors: Jia
authors: Division of Quantum Phases &devices, Department of Physics, Konkuk University, Seoul, 143-701, Korea.
authors: Minwoo
authors: M
authors: Park
authors: Division of Quantum Phases &devices, Department of Physics, Konkuk University, Seoul, 143-701, Korea.
authors: Hoonkyung
authors: H
authors: Lee
authors: Division of Quantum Phases &devices, Department of Physics, Konkuk University, Seoul, 143-701, Korea.
authors: Bae Ho
authors: BH
authors: Park