Faria Junior, Paulo E. and Fabian, Jaroslav (2023) Signatures of Electric Field and Layer Separation Effects on the Spin-Valley Physics of MoSe₂/WSe₂ Heterobilayers: From Energy Bands to Dipolar Excitons. NANOMATERIALS, 13 (7): 1187. ISSN 2079-4991
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Multilayered van derWaals heterostructures based on transition metal dichalcogenides are suitable platforms on which to study interlayer (dipolar) excitons, in which electrons and holes are localized in different layers. Interestingly, these excitonic complexes exhibit pronounced valley Zeeman signatures, but how their spin-valley physics can be further altered due to external parameters-such as electric field and interlayer separation-remains largely unexplored. Here, we perform a systematic analysis of the spin-valley physics in MoSe2/WSe2 heterobilayers under the influence of an external electric field and changes of the interlayer separation. In particular, we analyze the spin (S-z) and orbital (L-z) degrees of freedom, and the symmetry properties of the relevant band edges (at K, Q, and G points) of high-symmetry stackings at 0 degrees(R-type) and 60 degrees (H-type) angles-the important building blocks present in moire or atomically reconstructed structures. We reveal distinct hybridization signatures on the spin and the orbital degrees of freedom of low-energy bands, due to the wave function mixing between the layers, which are stacking-dependent, and can be further modified by electric field and interlayer distance variation. We find that H-type stackings favor large changes in the g-factors as a function of the electric field, e.g., from 5 to 3 in the valence bands of the H-h(h) stacking, because of the opposite orientation of S-z and L-z of the individual monolayers. For the low-energy dipolar excitons (direct and indirect in k-space), we quantify the electric dipole moments and polarizabilities, reflecting the layer delocalization of the constituent bands. Furthermore, our results show that direct dipolar excitons carry a robust valley Zeeman effect nearly independent of the electric field, but tunable by the interlayer distance, which can be rendered experimentally accessible via applied external pressure. For the momentum-indirect dipolar excitons, our symmetry analysis indicates that phonon-mediated optical processes can easily take place. In particular, for the indirect excitons with conduction bands at the Q point for H-type stackings, we find marked variations of the valley Zeeman (similar to 4) as a function of the electric field, which notably stands out from the other dipolar exciton species. Our analysis suggests that stronger signatures of the coupled spin-valley physics are favored in H-type stackings, which can be experimentally investigated in samples with twist angle close to 60ffi. In summary, our study provides fundamental microscopic insights into the spin-valley physics of van derWaals heterostructures, which are relevant to understanding the valley Zeeman splitting of dipolar excitonic complexes, and also intralayer excitons.
| Item Type: | Article |
|---|---|
| Uncontrolled Keywords: | INDIRECT INTERLAYER EXCITONS; WAALS; GRAPHENE; POLARIZATION; MOS2; valley Zeeman; spin-valley; van der Waals heterostructure; TMDC |
| Subjects: | 500 Science > 530 Physics |
| Divisions: | Physics > Institute of Theroretical Physics > Chair Professor Richter > Group Jaroslav Fabian |
| Depositing User: | Dr. Gernot Deinzer |
| Date Deposited: | 27 Feb 2024 07:34 |
| Last Modified: | 27 Feb 2024 07:34 |
| URI: | https://pred.uni-regensburg.de/id/eprint/59079 |
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