Condensed Matter Seminar "Correlative near-field and Raman imaging for twisted 2D materials"
Novel 2D materials (2DMs), a class of electronic single/few-layer lattices, demonstrate a number of unique physical effects. Among those, their electronic properties were shown to depend on the stacking order of the individual layers, specifically on their angular registry aka twist. Intuitively clear picture bases on translation superlattice formed by twisted lattices, also known as Moire-lattice. Splash of interest to twisted 2DM (including but not limited to graphene multi-layers) is due to both their unusual chiral electronic/optical properties and potential for applications in biosensing, electronics and quantum information technology. This work focuses on graphene samples with 2+ layers, where plasmonic response varies with the twist angle. Since electronic/optical properties of twisted 2DMs can be modulated at the scale of a few nanometers, the characterization methods with both high spatial resolution and capability to detect optical modulation are required. Scattering-type scanning near-field optical microscope (sSNOM) will be shown to reveal such properties of twisted graphene, in particular phonon-plasmon polariton coupling. Furthermore, correlation of hyperspectral sSNOM data (that is taken at multiple excitation) to confocal Raman scattering microscopy data will be shown to lead to explicit chirality identification. Potential avenues for expanding this technique to big-data analysis will be discussed.