3D Localized Trions in Monolayer WSe₂ in a Charge Tunable van der Waals Heterostructure

Abstract

Monolayer transition metal dichalcogenides (TMDCs) have recently emerged as a host material for localized optically active quantum emitters that generate single photons. (1-5) Here, we investigate fully localized excitons and trions from such TMDC quantum emitters embedded in a van der Waals heterostructure. We use direct electrostatic doping through the vertical heterostructure device assembly to generate quantum confined trions. Distinct spectral jumps as a function of applied voltage bias, and excitation power-dependent charging, demonstrate the observation of the two different excitonic complexes. We also observe a reduction of the intervalley electron-hole exchange interaction in the confined trion due to the addition of an extra electron, which is manifested by a decrease in its fine structure splitting. We further confirm this decrease of exchange interaction for the case of the charged states by a comparative study of the circular polarization resolved photoluminescence from individual excitonic states. The valley polarization selection rules inherited by the localized trions will provide a pathway toward realizing a localized spin-valley-photon interface.

Coulomb blockade in an atomically thin quantum dot coupled to a tunable Fermi reservoir

“…4). Conversely, for X 1− and X 1+ (at V g < −9 V and V g > 16 V, respectively) we observe a single spectral line, in contrast to a previous report 23 . The inset in Fig.…”

Identifying defect-related quantum emitters in monolayer WSe2

“…In addition, the single photon emission has been realized with several approaches, such as heterostructures driven electrically [13], nanoscale strain engineering [14][15][16][17] and sub-nm focused helium ion irradiation [18], which are mostly defect related. Meanwhile, the properties of such a 2D host of quantum emitters have been intensely investigated, including 3D localized trions in heterostuctures [19], manipulation of fine structure splitting (FSS) [20] and photon-phonon interaction [21]. Furthermore, the optical initialization of a single spin-valley in charged WSe 2 quantum dots [22] and the ability to deterministically load either a single electron or single hole into a Van der Waals heterostructure quantum device via a Coulomb blockade [23] have been demonstrated, which enable a new class of quantum-confined spin system to store and process information.…”

Hyperfine interaction in atomically thin transition metal dichalcogenides

“…However, novel opportunities are also opening in zerodimensional systems, like quantum dots based on TMD MLs [27,28]. Such structures seem to be more appropriate for the applications in the optoelectronic devices [29][30][31][32] and potentially easier to realize. Indeed, any disorder in 2D structures leads to the localization of the charge carrier wavefunction [33][34][35], which increases the spin and valley coherence times.…”