Lasing of Moiré Trapped MoSe$_2$/WSe$_2$ Interlayer Excitons Coupled to a Nanocavity

Qian, Chenjiang; Troue, Mirco; Figueiredo, Johannes; Soubelet, Pedro; Villafañe, Viviana; Beierlein, Johannes; Klembt, Sebastian; Stier, Andreas V.; Höfling, Sven; Holleitner, Alexander W.; Finley, Jonathan J.

doi:10.48550/arxiv.2302.07046

Cited by 2 publications

(2 citation statements)

References 17 publications

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“…These different g-factors originate from different stackings, and distinct dipolar exciton species can be observed in the crossover region between deep and shallow moiré potentials, as a function of the twist angle or temperature; however, no systematic experimental study has been realized to explore such conditions. We emphasize that our calculated values are in excellent agreement with previously reported theoretical studies [ 57 , 64 , 67 , 80 ], and lie within the available experimental values, which range from −15 to −17 in H-type stackings [ 20 , 47 , 48 , 49 , 50 , 51 , 53 , 60 , 61 ], and from 5 to 8 in R-type stackings [ 20 , 42 , 48 , 49 , 50 , 51 , 116 , 117 ].…”

Section: Low-energy Dipolar Excitonssupporting

confidence: 92%

Signatures of Electric Field and Layer Separation Effects on the Spin-Valley Physics of MoSe2/WSe2 Heterobilayers: From Energy Bands to Dipolar Excitons

Faria

Fabian

2023

Nanomaterials

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Multilayered van der Waals 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 (Sz) and orbital (Lz) degrees of freedom, and the symmetry properties of the relevant band edges (at K, Q, and Γ points) of high-symmetry stackings at 0° (R-type) and 60° (H-type) angles—the important building blocks present in moiré 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 Hhh stacking, because of the opposite orientation of Sz and Lz 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 (∼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 60°. In summary, our study provides fundamental microscopic insights into the spin-valley physics of van der Waals heterostructures, which are relevant to understanding the valley Zeeman splitting of dipolar excitonic complexes, and also intralayer excitons.

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Section: Low-energy Dipolar Excitonssupporting

confidence: 92%

Signatures of Electric Field and Layer Separation Effects on the Spin-Valley Physics of MoSe2/WSe2 Heterobilayers: From Energy Bands to Dipolar Excitons

Faria

Fabian

2023

Nanomaterials

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“…The prolonged values of IX dephasing times would be critical for the applications of quantum information science as well as the development of two-dimensional material-based nanolasers 47 .…”

Section: Resultsmentioning

confidence: 99%

Prolonged dephasing time of ensemble of moiré-trapped interlayer excitons in WSe2-MoSe2 heterobilayers

Durmuş

Demiralay

Sarpkaya

2023

Preprint

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The moiré superlattices of transition metal dichalcogenide heterobilayers have a pronounced effect on the optical properties of interlayer excitons (IXs) and have been intensively studied in recent years. However, the impact of the moiré potentials on the temporal coherence of the IXs has not yet been investigated in detail. Here, we systematically investigate the coherence properties of both the ensemble of delocalized IXs and the ensemble of localized IXs trapped in moiré potentials of the hexagonal boron nitride encapsulated WSe2-MoSe2 heterostructures. Our low-temperature first-order correlation measurements show that prolonged T2 dephasing times with values up to 700 fs can be obtained from the ensemble of localized IXs under moderate pump powers. We observed up to a fourfold increase over the values we obtained from the delocalized IXs, while a twofold over the previously reported values of T2~300 fs from the delocalized IXs. The prolonged values of T2 dephasing times and narrow photoluminescence (PL) line widths for the ensemble of moiré-trapped IXs compared to delocalized one indicate that dephasing mechanisms caused by exciton-low energy acoustic phonon and exciton-exciton scattering are significantly suppressed due to the presence of localization potentials. Our results show that ultra-long dephasing times can be expected if the dephasing time measurements are performed with the narrow photoluminescence emission line of a single moiré-trapped IX at a low pump power regime. The prolonged values of IX dephasing times would be critical for the applications of quantum information science and the development of two-dimensional material-based nanolasers.

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Lasing of Moiré Trapped MoSe$_2$/WSe$_2$ Interlayer Excitons Coupled to a Nanocavity

Cited by 2 publications

References 17 publications

Signatures of Electric Field and Layer Separation Effects on the Spin-Valley Physics of MoSe2/WSe2 Heterobilayers: From Energy Bands to Dipolar Excitons

Signatures of Electric Field and Layer Separation Effects on the Spin-Valley Physics of MoSe2/WSe2 Heterobilayers: From Energy Bands to Dipolar Excitons

Prolonged dephasing time of ensemble of moiré-trapped interlayer excitons in WSe2-MoSe2 heterobilayers

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