Creation of Single-Photon Emitters in WSe₂ Monolayers Using Nanometer-Sized Gold Tips

Abstract

Due to their tunable bandgaps and strong spin-valley locking, transition metal dichalcogenides constitute a unique platform for hosting single-photon emitters. Here, we present a versatile approach for creating bright single-photon emitters in WSe2 monolayers by the deposition of gold nanostars. Our molecular dynamics simulations reveal that the formation of the quantum emitters is likely caused by the highly localized strain fields created by the sharp tips of the gold nanostars. The surface plasmon modes supported by the gold nanostars can change the local electromagnetic fields in the vicinity of the quantum emitters, leading to their enhanced emission intensities. Moreover, by correlating the emission energies and intensities of the quantum emitters, we are able to associate them with two types of strain fields and derive the existence of a low-lying dark state in their electronic structures. Our findings are highly relevant for the development and understanding of single-photon emitters in transition metal dichalcogenide materials.

Prospects and challenges of quantum emitters in 2D materials

“…3(b)), with purities reaching as high as 95% and detection rates up to 10 kHz; however, a withstanding challenge was that emitters were still appearing in a large spectral range of 720-800 nm, and also, these emitters were limited to cryogenic temperatures. Other strain-engineering methods have been explored following these demonstrations, such as metallic nano-cubes 42 and nano-particles 43 , nano-indentation with AFM tips 44 , and electrically controlled microcantilevers 45 . While each of these approaches have advantages, such as dynamical control over the extent of strain 45 or concurrently achieving Purcell enhancement 42,43 , overall, the emitters' purities were not comparable to nano-pillar approaches 31,32 .…”

“…Other strain-engineering methods have been explored following these demonstrations, such as metallic nano-cubes 42 and nano-particles 43 , nano-indentation with AFM tips 44 , and electrically controlled microcantilevers 45 . While each of these approaches have advantages, such as dynamical control over the extent of strain 45 or concurrently achieving Purcell enhancement 42,43 , overall, the emitters' purities were not comparable to nano-pillar approaches 31,32 . For each of these approaches to strain engineering, control over the SPE emission energy has not been demonstrated, and SPEs appear across a large distribution of energies.…”

Trapping Interlayer Excitons in van der Waals Heterostructures by Potential Arrays

“…(iv) To account for the trapping-induced changes in the recombination lifetimes, τ 2D , [18,22,35] we adapt the concept of 2D exciton coherence area which is determined by exciton scattering. [36,37] From this model, we find that the exciton radiative lifetime is dependent on the exciton coherence radius r c , oscillator strength f 0 , and temperature T ,…”

“…[16,17] Moreover, the strong repulsive dipole-dipole interactions among IXs can be engineered by confining them in potential traps created by strains, disorders or moiré potentials, [18][19][20] which may provide rich opportunities * xuedan.ma@anl.gov for the study of quantum optical nonlinearities and creation of quantum photon sources. [21][22][23] While great strides have been made in trapping IXs in TMDs using strains and moiré potentials, [18,20,24,25] the influence of the potential trap nature, such as the trap geometries and densities, on the related photodynamics of the IXs including their trapping and localization remain largely unexplored. Specifically, upon excitation of TMD heterostructures, IXs can be formed over picosecond timescales.…”

Fluorescence blinking in MoS2 atomic layers by single photon energy transfer

“…For instance, single atom defects in 2D materials have been demonstrated to act as single photon emitters upon photon excitation [21][22][23][24] , which provide the essential element for quantum communication and computing based on 2D materials. Besides, artificially constructed TMDCs layers by the introduction of nanobubble 25 , wrinkles 26 , nanometersized gold tips 27 or pattern arrays of nanopillars 28,29 , have also been reported to behave as single photon sources in local strained areas due to the strain induced local confinement of excitons. These TMDCs materials provide a scalable platform for quantum photonic applications in a relatively controlled manner.…”