Fig. 5: WSe2-(MoS2-WSe2)3-MoS2 superlattices with boosted quadrupolar interlayer excitons (IXs) emission.
a The PL spectra and fitting curves with Viogt function of 2L (WSe2/MoS2), 3L (MoS2/WSe2/MoS2 and WSe2/MoS2/WSe2), and 4L (WSe2/MoS2/WSe2/MoS2), measured at 78 K and under laser excitation at 2.58 eV, 8.65 μW. The orange/blue circles with “+/–” symbols represent holes and electrons in different layers, respectively. PL spectra with different excitation powers for 2L WSe2/MoS2 (b) and 3L MoS2/WSe2/MoS2 (c), measured at 78 K and under laser excitation at 2.58 eV. Optical microscopy image (d) and steady-state spatial PL mapping of lower energy IXs (0.95–0.97 eV, quadrupolar IXs) (e) and higher energy IXs (1.09–1.12 eV, dipolar IXs) (f) for as-prepared 4L superlattice, measured at 78 K and under laser excitation at 2.58 eV with a galvo-scanning system with a step size of 1.2 μm, 78.8 μW. The solid blue, green, and red solid lines mark the 2L, 3L (MoS2/WSe2/MoS2), and 4L regions, respectively. g Schematic illustration of excitonic species in 8L WSe2-(MoS2-WSe2)3-MoS2 superlattice, including intralayer exciton, dipolar IX, and quadrupolar IX. h Transmission spectra of MoS2 monolayer, WSe2 monolayer, WSe2/MoS2 heterobilayer, and the WSe2-(MoS2-WSe2)3-MoS2 superlattice. The dashed lines represent the A exction peak energy of monolayer WSe2 and MoS2, respectively. i Low-temperature PL spectra in the second near-infrared region (NIR-II) region, measured at 78 K and under laser excitation at 2.33 eV, 0.782 mW. Data vertically offset for visualization in (a–c, i).
