Probing Interface-Driven Mechanisms of Non-Classical Light in van der Waals Heterostructures

Abstract

Single-photon emitters in two-dimensional semiconductors offer a versatile platform for integrated quantum photonics, yet their performance is strongly influenced by local dielectric environments and substrate-induced disorder. Here, we examine SPEs in monolayer WSe$_2$ incorporated into hBN/WSe$_2$/Clinochlore van der Waals heterostructures and assess how interface-mediated dielectric modulation governs their optical and quantum characteristics. Low-temperature micro-photoluminescence reveals narrow emission lines (100 - 300 $μ$eV) and robust non-classical behavior, with $g^{(2)}(0) = 0.13 \pm 0.02$ on SiO$_2$ and $0.54 \pm 0.02$ for emitters directly coupled to Clinochlore. Magneto-optical measurements yield effective g-factors near -8, consistent with defect states hybridized with dark excitons. WSe$_2$ on Clinochlore exhibits up to a fivefold enhancement in emission intensity, attributed to coupling with Fe-related substrate states that introduce resonant absorption near 1.75 eV. Kelvin probe force microscopy confirms strong dielectric contrast across thin and thick Clinochlore regions. Time-resolved photoluminescence shows that emitters on SiO$_2$ display a single $\approx 4$ ns lifetime, whereas those on Clinochlore exhibit biexponential dynamics with sub-nanosecond and tens-of-nanoseconds decay components. A phenomenological model incorporating coupling to bright and dark Fe-related states in Clinochlore accounts for modified excitation pathways. These results establish interface dielectric engineering in vdW heterostructures as an effective strategy for tailoring the radiative dynamics and brightness of quantum emitters in atomically thin materials.

Figures (5)

• Figure 1: (a) Schematic view of a van der Waals heterostructure stacked on SiO$_2$/Si substrate. (b) Optical image of the architecture illustrated in (a). (c) Lamellar structure of hBN, WSe$_2$ and Clinochlore, respectively. (d)$\mu$PL response at 4 K extracted from regions A (Thick-Clinochlore substrate), A' (Thin-Clinochlore substrate), and B (SiO$_2$ substrate), as indicated in (a). The PL intensity increases up to 5 times depending on the Clinochlore thickness compared with the bare SiO$_2$ substrate.
• Figure 2: $\mu$PL and magneto-PL measurements. Results of (a) power- dependent and (b) polarization-dependent characterization revealing an FSS of $\sim700~\mu\text{eV}$. (c) PLE studies, in which the spectrum shown in the upper panel was extracted under excitation energy of 1.72 eV (see dashed line in the lower part) while the color-map shows the emission response of several SPEs under an excitation energy range from 1.65 to 1.77 eV. (d) Color-coded map of the circularly polarized PL intensity of WSe$_2$/Clinochlore as a function of magnetic field. The dashed lines indicate the PL peak energy as a function of the magnetic field. The circularly polarized PL spectra ($\sigma^-$ for positive magnetic fields) were recorded at 3.6 K using a linearly polarized laser excitation with an energy of 1.88 eV PL spectra of WSe$_2$/Clinochlore for selected perpendicular magnetic fields. The labels P1 and X$^{0}$ indicate the peak emission of defect-states bound to an exciton and the neutral bright exciton peak, respectively.
• Figure 3: Second-order autocorrelation function under CW excitation revealing a photon antibunching value of $g^{(2)}(0) = 0.13 \pm 0.02$, $0.48 \pm 0.02$ and $0.54 \pm 0.02$, for substrates of SiO$_2$, thin Clinochlore, and thick Clinochlore, respectively. The horizontal dashed line indicates the SPE classical limit $g^{(2)}(0) = 0.5$.
• Figure 4: Dielectric contrast of the hBN/WSe$_2$/Clinochlore heterostructure probed by KPFM. (a) Optical microscopy image of a selected region from Fig. \ref{['fig1']}a, with its corresponding (b) schematic of the stacked bottom Clinochlore (light yellow shade for the thin region and dark yellow shade for the thick region), WSe$_2$ (red shade), and top hBN (green shade). The A and A' regions correspond to heterostructure regions formed by hBN/WSe$_2$/thick-Clinochlore and hBN/WSe$_2$/thin-Clinochlore, respectively, while the B and B' regions correspond to hBN/thick-Clinochlore and hBN/thin-Clinochlore. The local capacitor formed by the stacking of the distinct dielectrics is depicted on the right side for regions A and A'. (c) Topography and (d) CPD images of the selected heterostructure region acquired simultaneously by single-pass scan KPFM at $<2\%$ relative humidity.
• Figure 5: TRPL experimental results and decay model of our quantum emitters. (a) For region B a mono-exponential decay $e^{-\gamma_\mathrm{SPE}t}$ is observed. For regions A' and A, a biexponential decay is fitted using Eq. \ref{['eq: solution for SPE decay']}. Uncertainties for the fitting parameters are given in the SI. The data is normalized such that $A_1+A_2 = 1$. (b) Sketch of the proposed emission process: optical excitation populates a bright Fe-related state in Clinochlore, which relaxes non-radiatively into an energetically lower dark Clinochlore state. This dark state couples to the SPE in WSe2 with a rate $g$, while the SPE decays with $\gamma_\mathrm{SPE}$ and the dark Clinochlore state with $\gamma_\mathrm{Cl}$.