Exploration of exciton behavior in atomically thin WS2 layers by ionic gating

He, Xin; Zhang, Zehui; Zhang, Chenhui; Yang, Yang; Hu, Ming; Ge, Weikun; Zhang, Xixiang

doi:10.1063/1.5022327

Cited by 5 publications

(4 citation statements)

References 32 publications

(42 reference statements)

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“…Ionic liquid (IL) gating has been widely used in 2D materials due to its high efficiency in tuning carrier density [24,25]. It has been central to the exploration of the electronic and optical properties [26][27][28][29], for the tuning and realization of voltage-controlled superconductivity [30], and manipulation of the magnetic properties [31]. These studies all prove that IL gating is a mature and reliable technique.…”

Section: Introductionmentioning

confidence: 99%

Spin transport in multilayer graphene away from the charge neutrality point

Wen²,

Zhang³

et al. 2021

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Graphene is considered as a promising material in spintronics due to its long spin relaxation time and long spin relaxation length. However, its spin transport properties have been studied at low carrier density only, beyond which much is still unknown. In this study, we explore the spin transport and spin precession properties in multilayer graphene at high carrier density using ionic liquid gating. We find that the spin relaxation time is directly proportional to the momentum relaxation time, indicating that the Elliott-Yafet mechanism still dominates the spin relaxation in multilayer graphene away from the charge neutrality point.

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Section: Introductionmentioning

confidence: 99%

Spin transport in multilayer graphene away from the charge neutrality point

Wen²,

Zhang³

et al. 2021

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“…In conventional QCSE structures, current techniques used to obtain blue shift are mainly electrostatic doping [50][51][52] or relying on the asymmetry of the quantum well structure. 53 Change in doping alters the screening of the charges and in turn modulates the peak position.…”

Section: Resultsmentioning

confidence: 99%

Anomalous Stark Shift of Excitonic Complexes in Monolayer Semiconductor

Abraham,

Watanabe,

Taniguchi

et al. 2020

Preprint

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Monolayer transition metal dichalcogenide semiconductors host strongly bound twodimensional excitonic complexes, and form an excellent platform for probing manybody physics through manipulation of Coulomb interaction. Quantum confined Stark effect is one of the routes to dynamically tune the emission line of these excitonic complexes. In this work, using a high quality graphene/hBN/WS 2 /hBN/Au vertical heterojunction, we demonstrate for the first time, an out-of-plane electric field driven change in the sign of the Stark shift from blue to red for four different excitonic species, namely, the neutral exciton, the charged exciton (trion), the charged biexciton, and the defect-bound exciton. Such universal non-monotonic Stark shift with electric field arises from a competition between the conventional quantum confined Stark effect

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“…Reduced dimensionality together with reduced screening result in large exciton binding energies in the order of 0.5 eV in these semiconducting TMDCs [8][9][10]. There is an attractive Coulomb interaction between the bound electron and hole pair building an exciton and, as a consequence, the exciton binding energy can be manipulated with external stimuli such as strain [18], its dielectric environment [19,20], intense photoexcitation [21] or electron doping in field-effect structures [22,23]. Such external stimuli can cause band renormalization effects, counteracting the change in binding energy such that measured energies in optical interband experiments sensitive to the exciton ground states are only slightly changed with doping [24,25].…”

Section: Introductionmentioning

confidence: 99%

“…In a similar context, there is an ongoing debate in literature on the microscopic origin of the exciton manifold observed in photoluminescence (PL) spectra of monolayer (ML) WS 2 for which the lowest interband transition spin-forbidden. The corresponding spectral features are assigned in different studies to recombination of direct excitons, momentumforbidden and phonon-activated excitons, trion species (charged exciton), defect-related excitons and biexcitons [23,26]. A better understanding of the effect of doping on exciton formation, on electric field induced renormalization of electronic bands, electron-electron and electron-phonon interaction is of great interest for the interpretation and the control of optical properties of WS 2 monolayers.…”

Section: Introductionmentioning

confidence: 99%

Exciton Manifolds in Highly Ambipolar Doped WS2

et al. 2022

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The disentanglement of single and many particle properties in 2D semiconductors and their dependencies on high carrier concentration is challenging to experimentally study by pure optical means. We establish an electrolyte gated WS2 monolayer field-effect structure capable of shifting the Fermi level from the valence into the conduction band that is suitable to optically trace exciton binding as well as the single-particle band gap energies in the weakly doped regime. Combined spectroscopic imaging ellipsometry and photoluminescence spectroscopies spanning large n- and p-type doping with charge carrier densities up to 1014 cm−2 enable to study screening phenomena and doping dependent evolution of the rich exciton manifold whose origin is controversially discussed in literature. We show that the two most prominent emission bands in photoluminescence experiments are due to the recombination of spin-forbidden and momentum-forbidden charge neutral excitons activated by phonons. The observed interband transitions are redshifted and drastically weakened under electron or hole doping. This field-effect platform is not only suitable for studying exciton manifold but is also suitable for combined optical and transport measurements on degenerately doped atomically thin quantum materials at cryogenic temperatures.

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Exploration of exciton behavior in atomically thin WS2 layers by ionic gating

Cited by 5 publications

References 32 publications

Spin transport in multilayer graphene away from the charge neutrality point

Spin transport in multilayer graphene away from the charge neutrality point

Anomalous Stark Shift of Excitonic Complexes in Monolayer Semiconductor

Exciton Manifolds in Highly Ambipolar Doped WS2

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