Stacking 2D materials to build van der Waals heterostructures provides an interesting approach toward creating artificial lattices with desired band structures and possible new functionalities. In transition metal dichalcogenide (TMD) monolayers the optical absorption is strong, but the transition energy cannot be tuned as the neutral exciton has essentially no out-of-plane static electric dipole. In contrast, for homo-bilayers systems hole delocalization over the bilayer is only allowed in 2H stacking and results in strong interlayer exciton absorption and also in a larger A-B exciton separation as compared to 3R bilayers [1,2]. GW+BSE calculation scheme confirm signatures of efficient interlayer coupling for 2H stacking for the MoS2 bilayer case [3], when theoretical investigations of interlayer exciton properties for others TMD bilayers show interesting features [4]. Besides, interlayer exciton transitions are widely tunable in applied electric fields [5] allowing to investigate the interaction between intra and interlayer excitons [6,7].

[1] I. Paradisanos et al., Nat. Commun. 11, 2391 (2020).
[2] Z. Li et al., Phys. Rev. B 106, 045411 (2022).
[3] I. C. Gerber et al., Phys. Rev. B 99, 035443 (2019).
[4] Z. Li et al., Phys. Rev. B 106, 045411 (2022).
[5] N. Leisgang et al., Nat. Nanotechnol. 15, 901 (2020).
[6] L. Spondfeldner et al., Phys. Rev. Lett. 129, 107401 (2022).
[7] S. Feng et al., arXiv:2212.14338 (2022)

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