CFN Colloquium

"From band gaps to bound excitons: disentangling optical transitions and localized emitters in TMDCs at nanoscale dimensions"

Presented by Jim Schuck, Associate Professor of Mechanical Engineering at Columbia University

Thursday, March 1, 2018, 4:00 pm — CFN, Bldg 735, Seminar Room, 2nd Floor

The emergence of two-dimensional (2D) monolayer transition metal dichalcogenides (ML-TMDC) as direct bandgap semiconductors has rapidly accelerated the advancement of room temperature, 2D optoelectronic devices. Optical excitations on the TMDCs manifest from a hierarchy of electrically tunable, Coulombic free-carrier and excitonic many-body phenomena. Investigating the fundamental interactions underpinning these phenomena presents challenges, however, due to a complex balance of competing optoelectronic effects and interdependent properties. We show how optical detection of bound- and free-carrier photoexcitations is used to directly quantify carrier-induced changes of the quasiparticle band gap and exciton binding energies [1]. Pushing to the nanoscale, we demonstrate that a model hybrid architecture, a nano-optical antenna and a ML-WSe2 nanobubble, activates the optical activity of BX states at room temperature and under ambient conditions. These results show that engineered bound-exciton functionality as, in this case, localized nanoscale light sources, can be enabled by an architectural motif that combines localized strain and a nano-optical antenna, laying out a possible path for realizing room-temperature single-photon sources in high-quality 2D semiconductors.

Hosted by: Matthew Sfeir

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