Anisotropic strain-induced soliton movement changes stacking order and band structure of graphene multilayers: implications for charge transport

The crystal structure of solid-state matter greatly affects its electronic properties. For example, in multilayer graphene, precise knowledge of the lateral layer arrangement is crucial, since the most stable configurations, Bernal and rhombohedral stacking, exhibit very different electronic properties. Nevertheless, both stacking orders can coexist within one flake, separated by a strain soliton that can host topologically protected states. Clearly, accessing the transport properties of the two stackings and the soliton is of high interest. However, the stacking orders can transform into one another, and therefore, the seemingly trivial question of how reliable electrical contact can be made to either stacking order can a priori not be answered easily. Here, we show that manufacturing metal contacts to multilayer graphene can move solitons by several μm, unidirectionally enlarging Bernal domains due to arising mechanical strain. Furthermore, we also find that during dry transfer of multilayer graphene onto hexagonal boron nitride, such a transformation can happen. Using density functional theory modeling, we corroborate that anisotropic deformations of the multilayer graphene lattice decrease the rhombohedral stacking stability. Finally, we have devised systematics to avoid soliton movement, and how to reliably realize contacts to both stacking configurations, which will aid to reliably access charge transport in both stacking configurations.
F.R.G., F.W., D.P., J.L., and R.T.W. acknowledge funding from the excellence initiative Nanosystems Initiative Munich (NIM), the Center for Nanoscience (CeNS) and the Solar Technologies go Hybrid (SolTech) initiative. We additionally acknowledge funding by the Deutsche Forschungsgemeinschaft (DFG, German Research Foundation) under Germany’s Excellence Strategy − EXC-2111−390814868 (MCQST) and EXC 2089/1−390776260.“ (e-conversion). We also thank Leonid S. Levitov, Nicola Mazzar,i and Nicolas Mounet for discussions and Jochen Feldmann for using his scanning Raman setup. R.G.-A., M.P., and A.A. thank the Project FIS2016-76617-P of the Spanish Ministry of Economy and Competitiveness MINECO, the Basque Government under the ELKARTEK project (SUPER), and the University of the Basque Country (Grant No. IT-756-13) for partial funding of this work. K.W. and T.T. acknowledge support from the Elemental Strategy Initiative conducted by the MEXT, Japan, A3 Foresight by JSPS and the CREST (JPMJCR15F3), JST.