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Research Highlights

Published: Thu, 02/08/2018 - 9:30am

Researchers from the Raschke group are lighting up dark excitons.

Specifically, the Raschke group developed a method to observe dark excitons in a 2D (i.e., a single layer of atoms) semiconductor at room temperature. This observation is an exciting development in the story of dark exciton applications, which includes quantum information processing and fundamental studies of complex semiconductor materials.

Bright excitons – which very rapidly emit light after forming – have long been used to probe materials and fundamental quantum processes. Now the Raschke group is seeking to make use of normally invisible dark excitons as well.

Dark excitons are bound electron-hole pairs that, unlike their bright exciton counterparts, face spin-forbidden transitions that prevent recombination through photon emission. Because these excitons are reluctant to emit a photon, they remain dark.

Darkness means stability: a dark exciton’s “photoluminescence lifetime and coherence time is a thousand times longer than that of a bright exciton,” says Kyoung-Duck Park, the lead graduate student on this project. These long lifetimes are what make dark excitons potential...

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