Experimental Observation of ABCB Stacked Tetralayer Graphene

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Abstract
In tetralayer graphene, three inequivalent layer stackings should exist; however, only rhombohedral (ABCA) and Bernal (ABAB) stacking have so far been observed. The three stacking sequences differ in their electronic structure, with the elusive third stacking (ABCB) being unique as it is predicted to exhibit an intrinsic bandgap as well as locally flat bands around the K points. Here, we use scattering-type scanning near-field optical microscopy and confocal Raman microscopy to identify and characterize domains of ABCB stacked tetralayer graphene. We differentiate between the three stacking sequences by addressing characteristic interband contributions in the optical conductivity between 0.28 and 0.56 eV with amplitude and phase-resolved near-field nanospectroscopy. By normalizing adjacent flakes to each other, we achieve good agreement between theory and experiment, allowing for the unambiguous assignment of ABCB domains in tetralayer graphene. These results establish near-field spectroscopy at the interband transitions as a semiquantitative tool, enabling the recognition of ABCB domains in tetralayer graphene flakes and, therefore, providing a basis to study correlation physics of this exciting phase.
Funding Information
  • RWTH Aachen University (rwth0716, rwth0742)
  • Ministerium f?r Innovation, Wissenschaft und Forschung des Landes Nordrhein-Westfalen
  • Deutsche Forschungsgemeinschaft (437214324, BE 2441/9-1, EXC 2004/1 - 390534769, SFB 917, SPP 2244, TA 848/7-1)
  • H2020 Future and Emerging Technologies (881603)
  • Baden-W?rttemberg Stiftung
  • Max Planck-New York City Center for Nonequilibrium Quantum Phenomena

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