Localized interlayer excitons in MoSe2-WSe2 heterostructures without a moiré potential – Nature Communications

The sample structure is comprised of a twist-angle aligned MoSe-WSe heterostructure as depicted in Fig. 1a (see "Methods"). In order to probe the dependence of the IX trapping on the moiré potential, we fabricated a device where half of the heterostructure has the TMD layers separated by bilayer hBN and the other half has the layers in direct contact (with no hBN spacer). The TMD layers are encapsulated in hBN, and a few layers graphene top gate (V) and graphite back gate (V) serves to independently control the charge density and external electric field experienced by the TMD layers. We used low temperature confocal PL spectroscopy to measure the spatial dependence of the IX emission photon energy (Fig. 1b). In the DC region of the device the IX photon energy is centered around 1.34 eV, consistent with R-type (near 0° twist) MoSe-WSe heterostructures. The hBN separated region shows higher energy PL centered around 1.42 eV. This 80 meV increase in the energy of the PL is in agreement with the suppression of the moiré potential by the insertion of bilayer hBN (see Supplementary Fig. 1). When the confocal pinhole was removed, PL from both regions could be detected when exciting on the higher energy hBN-separated region. Figure 1c shows co- and cross-circularly polarized PL when exciting the hBN-separated region with a 1.72 eV laser and detecting from both regions. Surprisingly, while the DC region shows the cross-circularly polarized PL, consistent with previous studies on R-type structures, the hBN-separated region shows mostly co-circularly polarized PL (see Supplementary Fig. 3 for similar data from another sample).

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