2017/06/28 by Kyoung-Duck Park, Tao Jiang, Genevieve Clark +2 · 1 citation
Engineering · Materials Science · Physics and Astronomy · #2D Materials and Applications #Biexciton #Decoupling (probability) #Dipole #Exciton #Molecular Junctions and Nanostructures #Photoluminescence #Purcell effect #Radiative transfer #Semiconductor #Spontaneous emission #Strong Light-Matter Interactions #cond-mat.mtrl-sci
paper · pdf · doi:10.1038/s41565-017-0003-0
arxiv created 2017/06/28 · openalex created_date 2017/07/14 · openalex publication_date 2017/11/17 · arxiv updated 2018/02/14 · openalex updated_date 2026/08/05
Excitons, Coulomb-bound electron and hole pairs, are elementary photo-excitations in semiconductors, that can couple directly to light through radiative relaxation. In contrast to these bright excitons, dark excitons X\rmD with anti-parallel electron spin polarization exist, with generally forbidden radiative emission. Because of their associated long lifetimes, these dark excitons are appealing candidates for quantum computing and opto-electronic devices. However, optical read-out and control of X\rmD states have remained a major challenge due to their decoupling from light. Here, we present a novel tip-enhanced nano-optical approach to precisely switch and programmably modulate the X\rmD emission even at room temperature. Using monolayer two-dimensional transition metal dichalcogenide (TMD) WSe\rm2 on a gold film as model system, we demonstrate ∼ 6 × 105-fold enhancement in dark exciton photoluminescence quantum yield. This is achieved by the unique coupling of the nano-optical antenna-tip to the dark exciton out-of-plane optical dipole moment, with an extraordinary Purcell factor of ≥ 2 × 103 of the tip-sample nano-cavity. Compared to the necessity of cryogenic temperatures and high magnetic fields in conventional approaches, our work provides a new way to harness excitonic properties in low-dimensional semiconductors and new strategies for quantum opto-electronic devices.