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arXiv · 2009.06328

Radiative control of localized excitons at room temperature with an ultracompact tip-enhanced plasmonic nano-cavity

Hyeongwoo Lee·Inki Kim·Chulho Park·Mingu Kang·Jungho Mun·Yeseul Kim·Markus B. Raschke·Mun Seok Jeong·Junsuk Rho·Kyoung-Duck Park
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Abstract

In atomically thin semiconductors, localized exciton (X$_L$) coupled to light shows single quantum emitting behaviors through radiative relaxation processes providing a new class of optical sources for potential applications in quantum communication. In most studies, however, X$_L$ photoluminescence (PL) from crystal defects has mainly been observed in cryogenic conditions because of their sub-wavelength emission region and low quantum yield at room temperature. Furthermore, engineering the radiative relaxation properties, e.g., emission region, intensity, and energy, remained challenging. Here, we present a plasmonic antenna with a triple-sharp-tips geometry to induce and control the X$_L$ emission of a WSe$_2$ monolayer (ML) at room temperature. By placing a ML crystal on the two sharp Au tips in a bowtie antenna fabricated through cascade domino lithography with a radius of curvature of <1 nm, we effectively induce tensile strain in the nanoscale region to create robust X$_L$ states. An Au tip with tip-enhanced photoluminescence (TEPL) spectroscopy is then added to the strained region to probe and control the X$_L$ emission. With TEPL enhancement of X$_L$ as high as ~10$^6$ in the triple-sharp-tips device, experimental results demonstrate the controllable X$_L$ emission in <30 nm area with a PL energy shift up to 40 meV, resolved by tip-enhanced PL and Raman imaging with <15 nm spatial resolution. Our approach provides a systematic way to control localized quantum light in 2D semiconductors offering new strategies for active quantum nano-optical devices.

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Hyeongwoo Lee, Inki Kim, Chulho Park, Mingu Kang, Jungho Mun, Yeseul Kim, Markus B. Raschke, Mun Seok Jeong, Junsuk Rho, Kyoung-Duck Park. 2020-09-14. Radiative control of localized excitons at room temperature with an ultracompact tip-enhanced plasmonic nano-cavity. https://arxiv.org/abs/2009.06328

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