*ITAMP Lunch Seminar* *Speaker:* You Zhou (Harvard University) *Date:* Thursday, February 22nd *Time:* 12:00-1:00 pm Includes Pizza. *Title: Exploring the bright and the dark side of excitons in atomically-thin semiconductors* *Abstract: **Atomically thin transition metal dichalcogenides (TMDs) have recently emerged as a new class of semiconductors which exhibit direct band gaps, strong spin-orbit coupling and excitonic effects. In this talk, we will explore the fundamental properties of the bright and dark excitons in TMDs. On the bright side, we will discuss how we improve the optoelectronic properties of TMDs and how these improvements lead to realization of novel optoelectronic devices, such as an atomically-thin electrically-tunable resonant mirror. On the dark side, we introduce a technique to probe the orientation of luminescent excitons in TMDs via near-field coupling to surface plasmon polaritons. This method allows us to directly observe nominally spin-forbidden dark excitons in certain TMDs.* *Location: *B-106 @ Center for Astrophysics (60 Garden Street) *Directions: *After entering the lobby of the CfA, turn right to enter the hallway of the B building. In the hallway, turn right again, B-106 will be at the end of the hallway on the left side.