Soliton-dependent plasmon reflection at bilayer graphene domain walls

• Published in: Nature materials 2016-08, Vol.15 (8), p.840-844
• Main Authors: Jiang, Lili, Shi, Zhiwen, Zeng, Bo, Wang, Sheng, Kang, Ji-Hun, Joshi, Trinity, Jin, Chenhao, Ju, Long, Kim, Jonghwan, Lyu, Tairu, Shen, Yuen-Ron, Crommie, Michael, Gao, Hong-Jun, Wang, Feng
• Format: Article
• Language: English
• Subjects: 136/117; 639/301/357/918/1054; 639/624/400/1021; Biomaterials; Condensed Matter Physics; Domain walls; Electrostatics; Graphene; Infrared; letter; Materials Science; Nanocomposites; Nanostructure; Nanotechnology; Optical and Electronic Materials; Optical properties; Optoelectronics; Plasmons; Reflection; Solitons; Two dimensional
• ISSN: 1476-1122; 1476-4660
• DOI: 10.1038/nmat4653

2D surface plasmon polaritons are used to probe the domain-wall solitons in bilayer graphene; near-field infrared nanoscopy reveals various domain-wall structures in mechanically exfoliated graphene bilayers. Layer-stacking domain walls in bilayer graphene are emerging as a fascinating one-dimensional system 1 , 2 , 3 , 4 , 5 , 6 , 7 , 8 , 9 , 10 , 11 that features stacking solitons 1 , 2 , 3 , 4 structurally and quantum valley Hall boundary states 5 , 6 , 7 , 8 , 9 , 10 , 11 electronically. The interactions between electrons in the 2D graphene domains and the one-dimensional domain-wall solitons can lead to further new quantum phenomena. Domain-wall solitons of varied local structures exist along different crystallographic orientations 1 , 2 , 12 , 13 , which can exhibit distinct electrical, mechanical and optical properties. Here we report soliton-dependent 2D graphene plasmon reflection at different 1D domain-wall solitons in bilayer graphene using near-field infrared nanoscopy. We observe various domain-wall structures in mechanically exfoliated graphene bilayers, including network-forming triangular lattices, individual straight or bent lines, and even closed circles. The near-field infrared contrast of domain-wall solitons arises from plasmon reflection at domain walls, and exhibits markedly different behaviours at the tensile- and shear-type domain-wall solitons. In addition, the plasmon reflection at domain walls exhibits a peculiar dependence on electrostatic gating. Our study demonstrates the unusual and tunable coupling between 2D graphene plasmons and domain-wall solitons.