Binding energies and spatial structures of small carrier complexes in monolayer transition-metal dichalcogenides via diffusion Monte Carlo

Mayers, Matthew Z.; Berkelbach, Timothy C.; Hybertsen, Mark S.; Reichman, David R.

doi:10.1103/physrevb.92.161404

Cited by 109 publications

(126 citation statements)

References 53 publications

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“…From Figure 2(c) this energy difference is 65 meV taking into account the small red shift of the XX/D peak after 2 kW/cm 2 . Recent theoretical calculations accurately predict the binding energies of excitons and trions within 2D materials, but they fail to do so for biexcitons [33][34][35][36][37][38][39] .The models predict that the biexciton is less strongly bound than the trion, in contradiction to experimental findings 25,27 . However, the models reconcile this discrepancy by suggesting that the experimentally observed states may actually be those of excited biexcitons, as opposed to ground state biexcitons 25 .…”

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confidence: 40%

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Room temperature observation of biexcitons in exfoliated WS2 monolayers

Paradisanos

Germanis

Pelekanos

et al. 2017

Applied Physics Letters

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Single layers of WS2 are direct gap semiconductors with high photoluminescence (PL) yield holding great promise for emerging applications in optoelectronics. The spatial confinement in a 2D monolayer together with the weak dielectric screening lead to huge binding energies for the neutral excitons as well as other excitonic complexes, such as trions and biexcitons whose binding energies scale accordingly. Here, we report on the existence of biexcitons in mechanically exfoliated WS2 flakes from 78 K up to room temperature. Performing temperature and power dependent PL measurements, we identify the biexciton emission channel through the superlinear behavior of the integrated PL intensity as a function of the excitation power density. On the contrary, neutral and charged excitons show a linear to sublinear dependence in the whole temperature range. From the energy difference between the emission channels of the biexciton and neutral exciton, a biexciton binding energy of 65-70 meV is determined. *Corresponding authors: gnk@materials.uoc.gr ; stratak@iesl.forth.gr 2 The interest on two-dimensional (2D) materials has been steadily increasing since the discovery of graphene, a material with fascinating properties and great potential for various applications 1 . Transition metal dichalcogenides (TMDs) with the form MX2 (M = Mo, W, Ti, etc and X = S, Se, Te) exhibit a structure very similar to that of graphene and have attracted significant attention of the scientific community 2-5 for a number of reasons. Among the most attractive features of TMD compounds is that their electronic properties can vary from metallic to those of a wide band gap semiconductor depending on the structure, composition and dimensionality, while their band structure can be easily tuned by applying stress 6 . Owing to such layer-dependent electronic structure, TMDs exhibit extraordinary optoelectronic properties 7,8 as well as potential for enhanced performance in applications such as photodetectors 9 , photovoltaics 10,11 and non-linear optical components 12 .Among their prominent optical properties, TMD monolayers show strong PL in the visible and near-infrared spectral range, due to the transition from indirect band gap semiconductors in their bulk and few-layer forms, to direct band gap semiconductors in the monolayer limit 13 . Besides this, the spatial confinement of carriers in a 2D monolayer lattice and the weak dielectric screening, give rise to unusually strong excitonic effects and high binding energies [14][15][16] . These properties favor the stability of a variety of excitonic quasiparticles with extremely large binding energies, including neutral excitons with binding energies of several hundred meV 17,18 , charged excitons (trions) was shown that the biexciton emission in WS2 can be electrically tuned 27 , which is of great importance for TMDs-based photonic devices.The unusually strong excitonic effects in TMDs strongly suggest an enhanced thermal stability of biexciton emission. While neutral and charged excitons have...

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confidence: 40%

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confidence: 99%

Room temperature observation of biexcitons in exfoliated WS2 monolayers

Paradisanos

Germanis

Pelekanos

et al. 2017

Applied Physics Letters

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“…Charge-carrier complexes play a particularly important role in the optoelec-tronic properties of layered and 2D materials. In the field of 2D materials, the DMC-calculated binding energies of trions [165][166][167] and the binding energies of larger complexes such as biexcitons and quintons (charged biexcitons) 154,168 have been reported, as have the DMC-calculated binding energies and VMC-calculated recombination rates of ion-bound charge carrier complexes in heterobilayers of transition-metal dichalcogenides. 169,170 2.…”

Section: Excitonic Complexesmentioning

confidence: 99%

Variational and diffusion quantum Monte Carlo calculations with the CASINO code

Needs

Towler

Drummond

et al. 2020

The Journal of Chemical Physics

119

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“…While a few experimental studies have reported the bound biexciton in monolayer TMDs, significant discrepancies between the measured2324252627 and calculated2829303132 binding energy remain, which may arise for several reasons. Experimentally, associating specific spectroscopic features with biexciton states can be extremely challenging.…”

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confidence: 99%

Neutral and charged inter-valley biexcitons in monolayer MoSe2

et al. 2017

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In atomically thin transition metal dichalcogenides (TMDs), reduced dielectric screening of the Coulomb interaction leads to strongly correlated many-body states, including excitons and trions, that dominate the optical properties. Higher-order states, such as bound biexcitons, are possible but are difficult to identify unambiguously using linear optical spectroscopy methods. Here, we implement polarization-resolved two-dimensional coherent spectroscopy (2DCS) to unravel the complex optical response of monolayer MoSe2 and identify multiple higher-order correlated states. Decisive signatures of neutral and charged inter-valley biexcitons appear in cross-polarized two-dimensional spectra as distinct resonances with respective ∼20 and ∼5 meV binding energies—similar to recent calculations using variational and Monte Carlo methods. A theoretical model considering the valley-dependent optical selection rules reveals the quantum pathways that give rise to these states. Inter-valley biexcitons identified here, comprising of neutral and charged excitons from different valleys, offer new opportunities for developing ultrathin biexciton lasers and polarization-entangled photon sources.

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Binding energies and spatial structures of small carrier complexes in monolayer transition-metal dichalcogenides via diffusion Monte Carlo

Cited by 109 publications

References 53 publications

Room temperature observation of biexcitons in exfoliated WS2 monolayers

Room temperature observation of biexcitons in exfoliated WS2 monolayers

Variational and diffusion quantum Monte Carlo calculations with the CASINO code

Neutral and charged inter-valley biexcitons in monolayer MoSe2

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