Spectroscopy and accurate spatial positioning of quantum emitters hosted by two-dimensional semiconductors

Abstract

Atomically-thin semiconductors offer intriguing technological advantages for quantum photonic applications. Advantages include a lack of dangling bonds, atomically-precise interfaces, the potential to design novel heterostructures with an absence of nuclear spins, and the ease of integration with photonic integrated chip platforms. These benefits offer a new opportunity to construct a scalable quantum architecture with a coherent lightmatter interface, an exciting prospect for future quantum technologies. This thesis takes the first steps in this direction. Atomically-thin flakes of transition metal dichalcogenides (WSe2 or MoSe2) are transferred to substrates with smooth and nanopatterned regions. Using cryogenic microphotoluminesce spectroscopy, a correlation between isolated quantum emitters and localised strain ‘pockets’ is observed. This observation is exploited to fabricate WSe2 arrays of highly pure single photon (g(2)(0) <0.5%) emitters at deterministic spatial positions (120±30 nm accuracy) with nearly 100% efficiency. The quantum emitters intrinsic optical properties are characterised via magnetic field and temperature dependent spectroscopy. The nanoscale strain engineering approach provides a universal scheme to create spatially and spectrally isolated quantum emitters in other two-dimensional materials. The thesis concludes with a discussion on the origin and dynamics of strain-tuned localized excitons in 2D semiconductors, presenting local disorder and exciton funnelling as important ingredients.