Past Events

The layered van der Waals material WTe₂ has recently attracted interested for being a topological semimetal, with type 2 Weyl points and extraordinary magnetoresistance at low temperatures. When thinned down to a monolayer we find that WTe₂ exhibits unusual properties, including gapless edge states. The properties of the edge states are consistent with their being the helical boundary modes of a two-dimensional topological (quantum spin Hall) insulator. The insulating state that develops in the sample interior is quite peculiar and may require electron-hole correlations to explain. Indications of several phase transitions are seen as a function of gate voltage and temperature, and further phenomena appear on going to two and more layers.                                                               
 

Coffee and tea will be served 20 minutes prior to the seminar.