Seminarium Fizyki Ciała Stałego

Raman spectroscopy is a technique of choice in studies of low dimensional materials and structures. This is due to its sensitivity to several factors such as e.g. strain or electron density. Even more information of those materials can be obtained if the excitation laser energy is in resonance with any appreciable joint density of electronic states. A plethora of new effects emerge in the resonant Raman scattering spectroscopy. Electronic structure of molybdenum disufide (MoTe2) provides an unique test-bed to study those effects, as the energy of light from a commonly used He-Ne laser coincides with van Hove singularity of MoTe2 electronic band-structure. Results of the resonant Raman scattering measurements will be discussed in this presentation. It will be shown how the resonance affects low-energy lattice excitations and the fine structure of the out-of-plane vibrations. The effect of temperature on the Raman scattering will be examined with two original effects: the complete quenching of the out-of-plane mode in 2-layer thick MoTe2 and the emergence of the fine structure in the mode, which corresponds to the bulk inactive B12g vibrations. Physics behind the observed effects will be contemplated.