Stacking-tailoring quasiparticle energies and interlayer excitons in bilayer Janus MoSSe

Abstract

Stacking sequence of bilayer van der Waals transition metal dichalcogenides determines their electronic and related optical excitations. When the Janus monolayer structure has been taken to construct bilayer TMDs, it would introduce another degree of freedom, the out-of-plane intrinsic dipole moment, to tune the electronic and optical properties. Here we reveal that the electronic band structures and interlayer excitons can be dramatically tuned via the stacking sequence of the bilayer MoSSe with the different intrinsic dipole orientations. Moreover, the lowest energy interlayer excitons exhibit diverse spatial extensions, and the corresponding radiative lifetimes can be tailored within the range of ∼10−8 to ∼10−2 seconds at room temperature, by means of optimizing the dipole orientation and stacking sequence, and when the dipole moment keeps the same orientation for the constituent layer, it will slower the radiative recombination. Our findings shed a light on the applications of the interlayer excitons in Janus MoSSe on optoelectronics.

Dipole moment and pressure dependent interlayer excitons in MoSSe/WSSe heterostructures

“…Previous work has shown that the sulfur group elements in each MXY monolayer play different roles in band structures, resulting in a variety of band structures under different stacking orders. 55,56 Therefore, it is of great significance to explore A large band offset is beneficial for electron-hole separation in heterostructures to obtain a longer lifetime of IX, while the intrinsic dipole moment in MoSSe/WSSe would increase the band offset furthermore. 57 The band offset and dipole moments of the three stacking configurations are shown in Table 1, and the dipole moments of the heterostructure composed of the 1T phase MoSSe and WSSe monolayers are also shown in Table S2.…”

Intrinsic Control of Interlayer Exciton Generation in Van der Waals Materials via Janus Layers

“…40 the intrinsic electric field, with a possible reordering of IP and IL excitons, was done recently for Janus-bilayers. 41 In this paper, we propose that combining a non-Janus TMD monolayer with a Janus monolayer�thus creating a TMD@ JTMD heterostructure�allows for reliable tuning of the relative order of the IP and IL excitons, in turn leading to an efficient pathway for IP-to-IL conversion via exciton−phonon scattering. Experimentally, Trivedi et al 42 have already shown the controllable room temperature fabrication and optical characterization of TMD@JTMD and JTMD@JTMD HBL crystals.…”

“…Janus monolayers have been experimentally demonstrated in samples with high structural and optical quality . A first theoretical prediction of the impact of the intrinsic electric field, with a possible reordering of IP and IL excitons, was done recently for Janus-bilayers . In this paper, we propose that combining a non-Janus TMD monolayer with a Janus monolayerthus creating a TMD@JTMD heterostructureallows for reliable tuning of the relative order of the IP and IL excitons, in turn leading to an efficient pathway for IP-to-IL conversion via exciton–phonon scattering.…”