DQMP FORUM: Rigid vibrations and spectroscopic fingerprints of layered materials (Marco Gibertini ) / Interacting Hall response in quantum gas experiments (Sebastian Greschner)

20.11.2018 13:00 – 14:00

Rigid vibrations and spectroscopic fingerprints of layered materials

Low-frequency vibrational modes in layered materials involve rigid relative motions of the layers that are classified as layer-breathing and layer-shear modes. When exfoliated into multilayer structures, the change in frequency of these modes with the number of layers provides a useful tool to characterize the system using Raman or infrared spectroscopy. Here we show how group theoretical arguments allow us to seamlessly predict spectroscopic fingerprints of all multilayers. We combine a description of the normal modes in terms of a one-dimensional mechanical model with symmetry arguments to disclose the evolution of the point group from the bulk to any multilayer. We elucidate effects on the equation of motion and on the connection between vibrational frequencies and elastic constants that arise when the multilayer belongs to a lower symmetry class than the bulk. Group theory is finally adopted to identify Raman active modes and reconstruct the fan diagram of any layered material.


Interacting Hall response in quantum gas experiments

Recent experiments with ultracold quantum gases in artificial magnetic fields have shown the possibility to study the Hall effect in quasi one-dimensional highly tunable ladder systems. In this context we theoretically analyze the properties of the reactive Hall response on ladder models with strongly interacting bosons and fermions. We compare different methods for the computation of the static Hall coefficient and discuss its dependence on the various methods or limits considered. In the cases relevant for recent experiments in synthetic dimensions, we find a surprising universal behavior of the weak field Hall coefficient of single component phases in the case of an SU(M) symmetric interaction.

Lieu

Bâtiment: Ecole de Physique

Auditoire Stückelberg

entrée libre