Abstract:   Symmetry and topology are two of the conceptual pillars that underlie our understanding of matter.   While both ideas are old, over the past several years a new appreciation of their interplay has led to dramatic progress in our understanding of topological electronic phases.  A paradigm that has emerged is that insulating electronic states with an energy gap fall into distinct topological classes.   Interfaces between different topological phases exhibit gapless conducting states that are protected and are impossible to get rid of. In this talk we will discuss the application of this idea to the quantum Hall effect, topological insulators,  topological semimetals and topological superconductors.  The latter case has led to the quest for observing Majorana fermions in condensed matter, which opens the door to proposals for topological quantum computation.  We will close by surveying the frontier of topological phases in the presence of strong interactions.

Please note: The Colloquim starts at 19:30 hours in the main auditorium of the Oort building. Before the Colloquium, there is a common dinner in the canteen located on the ground floor of the Oort building. This dinner starts at 18:00 hours sharp and is FREE of charge, under the condition that one attends the colloquium and that one has made a reservation before noon on the Tuesday preceding the colloquium. 

The registration form is only accessible from within the University (to block spammers); if you would like to register for the dinner from outside the University, please send an email to fran@lorentz.leidenuniv.nl   The revolving doors to the Oort building  are accessible until 9 pm after that they are locked and one should instead use the sliding doors directly adjacent to the Huygens building: these can be opened with an electronic key (seek help from locals).