Optical and vibrational properties of twisted 2D layered heterostructures

Principal investigator

Janina Maultzsch, Department of Physics, Friedrich-Alexander-Universität Erlangen-Nürnberg [webpage]

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Abstract

The aim of the project is to unravel interlayer interactions and electron-phonon coupling in twisted bilayers of van-der-Waals materials (TMDCs, graphene, antimony-based semiconductors) by optical spectroscopy. As the overlap of the electron wave functions between the layers depends on the energies and k-vectors of the corresponding states, we expect different levels of interlayer interaction, in TMDCs in particular at energies in the C- exciton range. These can be accessed by choosing appropriate excitation energies in Raman and photoluminescence (PL) spectroscopy. By investigating the excitation-energy and twist- angle dependence of interlayer phonon modes and PL emission, we will obtain insight into twist-angle dependent hybridization of electronic states, interlayer distance variations, and changes of structural symmetry.

Twisted 2D layered heterostructures are prepared by mechanical exfoliation and transfer techniques available in our lab, including encapsulation in hBN. In addition, MoS2 layers can be grown by chemical vapor deposition (CVD) in our group. If more advanced techniques for sample preparation are necessary, we will collaborate with other groups in the SPP. Our main experimental techniques include resonance Raman spectroscopy, in particular with excitation in the near-UV range, µ-photoluminescence (µ-PL), and tip-enhanced Raman- and PL spectroscopies for high lateral resolution. These methods will be available to interested other projects in the SPP2244.