Ultra‐Long Lifetimes of Single Quantum Emitters in Monolayer WSe₂/hBN Heterostructures

Abstract

Here, ultra‐long lifetimes of defect‐trapped single quantum emitters (SQEs) in monolayer WSe2/hBN heterostructures are reported. The lifetimes of these SQEs are approximately 225 ns, more than two orders of magnitude larger than what has been previously reported for defect‐trapped excitons in WSe2. These SQEs consist of co‐linearly polarized doublet peaks with a fine structure splitting of 0.45 meV. Second‐order correlation measurements show antibunched single‐photon emission with a g(2)(0) value of ≈0.13. Through numerical analysis and modeling, it is shown how such long‐lifetime single emitters can arise from bright and dark exciton coupling in antisite defects on the W sites. Additionally, high‐quality single‐photon emission over a wide range of lifetimes—from 2 ns to over 200 ns—is also reported, suggesting a variety of other possible defect structures present. The flexibility to generate high fidelity single‐photon emission, over a wide range of lifetimes in a single material system, has potential in many optical quantum computing applications from high‐bit‐rate single‐photon sources to quantum memory devices.

Advances in quantum light emission from 2D materials

“…Their excited state lifetime was measured to be of the order of a few nanoseconds, three orders of magnitude higher than the delocalized excitons. Recently, much longer lifetimes (>200 ns) were reported in defects in chemical vapor deposition (CVD)-grown WSe 2 that are encapsulated by hBN [25]. The PL intensity also exhibited saturation with increasing power, as expected for an atom-like emitter.…”

Defect and strain engineering of monolayer WSe2 enables site-controlled single-photon emission up to 150 K

“…While the engineering methods outlined in this work demonstrate the interplay between defects and strain, as predicted by the above-mentioned picture, the physical morphology of the defects responsible for SPE remains elusive. There is a lack of consensus of the defects responsible for single-photon emission, but they have been previously attributed to structures, including selenium vacancies 14 , tungsten centered vacancies 29 , oxygen interstitials 30 , and anti-site defects 31 . It is also plausible that multiple types of defects may be responsible for single-photon emission as long as they break the valley symmetry, and upon application of strain, introduce defect states with favorable energies close to the conduction band.…”

Bright single photon emitters with enhanced quantum efficiency in a two-dimensional semiconductor coupled with dielectric nano-antennas

“…This implies high nonradiative rates in this system (Γ nr > Γ r ). On the other hand, SPEs with PL lifetimes in the range of 100 ns were previously observed only in monolayer WSe 2 encapsulated in hexagonal boron nitride 12 , known for suppressing the nonradiative processes. In our case, possible causes for suppression of nonradiative decay could be the high surface quality of crystalline GaP structures, or that some SPEs are formed in the suspended parts of the monolayer in proximity to the near-field hotspots and between the pillars 8 .…”

“…ingle-photon emitters (SPEs) in two-dimensional (2D) semiconducting WSe 2 [1][2][3][4][5] open attractive perspectives for few-atom-thick devices for quantum technologies owing to favorable excitonic properties 6 and the integration with arbitrary substrates, including nanostructured surfaces 7,8 . Several theoretical models have been proposed to provide insight into the origin of SPEs observed in the cryogenic photoluminescence (PL) spectra of 2D WSe 2 [9][10][11][12] . Their occurrence was explained by the presence of strain-induced potential traps for excitons 9 , momentum-dark states 10 , or various types of defects 11,12 .…”

“…Several theoretical models have been proposed to provide insight into the origin of SPEs observed in the cryogenic photoluminescence (PL) spectra of 2D WSe 2 [9][10][11][12] . Their occurrence was explained by the presence of strain-induced potential traps for excitons 9 , momentum-dark states 10 , or various types of defects 11,12 . While the exact origin is still under debate, the first significant steps have been made to integrate WSe 2 SPEs in devices, including electroluminescent structures [13][14][15] , waveguides 16,17 , and tunable high-Q microcavities 18 .…”