Visualizing the response of topological materials under Coulomb and magnetic perturbations
Event details
| Date | 30.05.2016 |
| Hour | 11:00 |
| Speaker |
Dr. Paolo Sessi Experimentelle Physik II, Physikalisches Institut, Universität Würzburg |
| Location |
aquarium (PH L1 503)
|
| Category | Conferences - Seminars |
The recent discovery of materials hosting topologically protected electronic states opened a new era in condensed matter. Since topological properties usually manifest at boundaries, scanning probe techniques are ideal tools to visualize them with both high spatial and energy resolution. In my talk, I will report recent experiments that not only allow to visualize the presence of these unconventional boundary modes, but also to demonstrate some of their unusual properties. In particular, I will discuss recent efforts focused on the controlled manipulation of topological states once coupled to well-defined perturbations. I will first examine topological insulators and show that, contrary to what generally believed, magnetic order and gapless states can coexist. I will illustrate how this is intimately related to the dual nature of magnetic dopants, which leads to the emergence of a two-fluid behavior where the competition in between opposite trends, i.e. gap opening vs. gap-closing, is ultimately linked to the localized vs. delocalized nature of the perturbations-induced quasiparticles. I will then report more recent experiments on the new class of materials known as Weyl semimetals. The surfaces of these compounds host a new class of topologically protected electronic states that form Fermi arcs, which correspond to unclosed contours connecting Weyl points of opposite chirality. By quasi particle interference mapping, we detect the emergence of a rich scattering scenario. I will discuss how our experiments allow for a detailed verification of existing theoretical proposals dealing with intra- and inter-arc scattering events. More generally, I will discuss how electronic states propagate in these materials where the lack of inversion symmetry, combined with strong spin-orbit coupling, gives rise to a plethora of multi-band spin-split states.
Practical information
- Expert
- Free
Organizer
- Fabio Donati
Contact
- Fabio Donati