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Exploring the band structure of multilayer graphene

We have probed electronic excitations between Landau levels in freestanding N-layer graphene over a broad energy range, with unprecedented spectral and spatial resolution, using micro magneto-Raman scattering spectroscopy. A characteristic evolution of electronic bands in up to five Bernal-stacked graphene layers is evidenced and shown to remarkably follow a simple theoretical approach, based on an effective bilayer model. (N > 3)-layer graphenes appear as appealing candidates in the quest for novel phenomena, particularly in the quantum Hall effect regime. Our work paves the way toward minimally invasive investigations of magneto-excitons in other emerging low-dimensional systems, with a spatial resolution down to 1 μm.

 

Figure 1 : Dispersion of the electronic excitations in N-layer graphene. Parts a−e show false-color maps of the micro magneto-Raman scattering spectra of mono- to pentalayer graphene, as a function of the magnetic field, after subtraction of the spectrum recorded at B = 0 T. Horizontal light blue bars mask residual contributions from the G- and 2D-mode features in N-LG, near 1585 cm−1 , and 2700 cm−1 , respectively, and from the underlying Si substrate, near 1000 cm−1 . The corresponding peak frequencies of the electronic Raman features extracted from Lorentzian fits are shown in f−j. The peak frequencies are determined with an experimental error that is smaller than the symbol size. The solid lines are calculated dispersions of the Landau levels assuming a linear dispersion for monolayer graphene and using the effective bilayer model.

 

S. Berciaud et al., Nano Letters 14, 4548, (2014)