Edbert Sie (SIMES Seminar)

Date(s) - Nov 15 2016
10:00 AM - 11:00 AM

Room 335, McCullough Building


Optical tuning of electronic valleys

Edbert Sie
Massachusetts Institute of Technology

Monolayer transition-metal dichalcogenides are 2D semiconducting materials that exhibit many remarkable properties. They have a pair of electronic valleys whose index can serve as a new degree of freedom. These valleys are energetically degenerate, however it is desirable to split their energy levels to use them for practical valleytronic devices. Here, I will show that light can be used to achieve this in WS2 by means of the optical Stark effect. The resulting energy splitting achieved this way is remarkably high, comparable to using a hundred Tesla magnetic field. Apart from the optical Stark effect we also observed the so-called Bloch-Siegert shift, a delicate phenomenon that has eluded direct observation so far. Finally, I will show some results from our newly built tabletop time-resolved HHG ARPES with an unprecedented resolution and describe the future prospects of using this technique to manipulate the phases of matter.