Resonance Profiles of Valley Polarization in Single-Layer 
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Tornatzky, Hans; Kaulitz, Anne-Marie; Maultzsch, Janina

doi:10.1103/physrevlett.121.167401

Cited by 37 publications

(27 citation statements)

References 32 publications

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“…49 Scattering process involving zone boundary phonons are also believed to be responsible for the notorious valley depolarization, which represents a serious obstacle for valleytronics. [50][51][52] After we have confirmed that our approach based on DFT derived bandstructure and the model dielectric function defined in Eq. (2) adequately describes key elements of the photoemission and the EELS data in the energy region of the A and B-excitons we focus now on the momentum dependence of the C-exciton.…”

Section: Eelssupporting

confidence: 61%

Nonlocal dielectric function and nested dark excitons in MoS2

et al. 2019

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Their exceptional optical properties are a driving force for the persistent interest in atomically thin transition metal dichalcogenides such as MoS 2. The optical response is dominated by excitons. Apart from the bright excitons, which directly couple to light, it has been realized that dark excitons, where photon absorption or emission is inhibited by the spin state or momentum mismatch, are decisive for many optical properties. However, in particular the momentum dependence is difficult to assess experimentally and often remains elusive or is investigated by indirect means. Here we study the momentum dependent electronic structure experimentally and theoretically. We use angle-resolved photoemission as a one-particle probe of the occupied valence band structure and electron energy loss spectroscopy as a two-particle probe of electronic transitions across the gap to benchmark a single-particle model of the dielectric function ϵðq; ωÞ against momentum dependent experimental measurements. This ansatz captures key aspects of the data surprisingly well. In particular, the energy region where substantial nesting occurs, which is at the origin of the strong light-matter interaction of thin transition metal dichalcogenides and crucial for the prominent C-exciton, is described well and spans a more complex exciton landscape than previously anticipated. Its local maxima in ðq ≠ 0; ωÞ space can be considered as dark excitons and might be relevant for higher order optical processes. Our study may lead to a more complete understanding of the optical properties of atomically thin transition metal dichalcogenides.

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Section: Eelssupporting

confidence: 61%

Nonlocal dielectric function and nested dark excitons in MoS2

et al. 2019

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“…Another striking difference between TMD materials is the amplitude of spin/valley polarization for excitons. Although strong valley polarization and valley coherence have been measured in WSe 2 , WS 2 , and MoS 2 MLs, the polarization in MoSe 2 and MoTe 2 MLs is very weak 35,36 except under quasi-resonant excitation where significant polarization has been measured for the trion in MoSe 2 37 . Recently, it was proposed that a crossing of bright and dark exciton dispersion curves combined with a Rashba effect associated with local fluctuations of electric field can lead to very fast spin relaxation 11 .…”

Section: Discussionmentioning

confidence: 97%

Measurement of the spin-forbidden dark excitons in MoS2 and MoSe2 monolayers

et al. 2020

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Excitons with binding energies of a few hundreds of meV control the optical properties of transition metal dichalcogenide monolayers. Knowledge of the fine structure of these excitons is therefore essential to understand the optoelectronic properties of these 2D materials. Here we measure the exciton fine structure of MoS 2 and MoSe 2 monolayers encapsulated in boron nitride by magneto-photoluminescence spectroscopy in magnetic fields up to 30 T. The experiments performed in transverse magnetic field reveal a brightening of the spinforbidden dark excitons in MoS 2 monolayer: we find that the dark excitons appear at 14 meV below the bright ones. Measurements performed in tilted magnetic field provide a conceivable description of the neutral exciton fine structure. The experimental results are in agreement with a model taking into account the effect of the exchange interaction on both the bright and dark exciton states as well as the interaction with the magnetic field.

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“…The emitted light gives information on spin and valley dynamics in time-integrated PL experiments. The circular polarization, P c , in time-integrated experiments depends on the exact ratio of PL emission time τ PL to depolarization time (τ depol ) as P P = /(1 + ) τ τ c 0 PL depol , where P 0 is the initially generated polarization, which could depend on the excitation energy 169,170 .…”

Section: Spin-valley Polarizationmentioning

confidence: 99%