Negative Valley Polarization in Doped Monolayer MoSe2

Background: Two-dimensional (2D) transition-metal dichalcogenides (TMDCs) with intrinsically crystal inversion-symmetry breaking have shown many advanced optical properties. In particular, the valley polarization in 2D TMDCs that can be addressed optically has inspired new physical phenomena and great potential applications in valleytronics. Results: Here, we propose a TMDC–nanoantenna system that could effectively enhance and direct emission from the two valleys in TMDCs into diametrically opposite directions. By mimicking the emission from each valley of the monolayer of WSe2 as a chiral point-dipole emitter, we demonstrate numerically that the emission from different valleys is directed into opposite directions when coupling to a double-bar plasmonic nanoantenna. The directionality derives from the interference between the dipole and quadrupole modes excited in the two bars, respectively. Thus, we could tune the emission direction from the proposed TMDC–nanoantenna system by tuning the pumping without changing the antenna structure. Furthermore, we discuss the general principles and the opportunities to improve the average performance of the nanoantenna structure. Conclusion: The scheme we propose here can potentially serve as an important component for valley-based applications, such as non-volatile information storage and processing.

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Experimental observation of topological Z2 exciton-polaritons in transition metal dichalcogenide monolayers

Nature Communications ◽

10.1038/s41467-021-24728-y ◽

2021 ◽

Vol 12 (1) ◽

Author(s):

Mengyao Li ◽

Ivan Sinev ◽

Fedor Benimetskiy ◽

Tatyana Ivanova ◽

Ekaterina Khestanova ◽

...

Keyword(s):

Transition Metal ◽

Transition Metal Dichalcogenides ◽

Transition Metal Dichalcogenide ◽

Strong Light ◽

Strongly Coupled ◽

Exciton Polaritons ◽

Valley Polarization ◽

Topological States ◽

Metal Dichalcogenides ◽

Quantum Science

AbstractThe rise of quantum science and technologies motivates photonics research to seek new platforms with strong light-matter interactions to facilitate quantum behaviors at moderate light intensities. Topological polaritons (TPs) offer an ideal platform in this context, with unique properties stemming from resilient topological states of light strongly coupled with matter. Here we explore polaritonic metasurfaces based on 2D transition metal dichalcogenides (TMDs) as a promising platform for topological polaritonics. We show that the strong coupling between topological photonic modes of the metasurface and excitons in TMDs yields a topological polaritonic Z2 phase. We experimentally confirm the emergence of one-way spin-polarized edge TPs in metasurfaces integrating MoSe2 and WSe2. Combined with the valley polarization in TMD monolayers, the proposed system enables an approach to engage the photonic angular momentum and valley and spin of excitons, offering a promising platform for photonic/solid-state interfaces for valleytronics and spintronics.

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Electrically switchable valley polarization, spin/valley filter, and valve effects in transition-metal dichalcogenide monolayers interfaced with two-dimensional ferromagnetic semiconductors

Physical Review B ◽

10.1103/physrevb.104.l201403 ◽

2021 ◽

Vol 104 (20) ◽

Author(s):

Ao Zhang ◽

Kaike Yang ◽

Yun Zhang ◽

Anlian Pan ◽

Mingxing Chen

Keyword(s):

Transition Metal ◽

Ferromagnetic Semiconductors ◽

Transition Metal Dichalcogenide ◽

Two Dimensional ◽

Valley Polarization

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Valley Orientation of Electrons and Excitons in Atomically Thin Transition Metal Dichalcogenide Monolayers (Brief Review)

JETP Letters ◽

10.1134/s0021364021010033 ◽

2021 ◽

Vol 113 (1) ◽

pp. 7-17

Author(s):

M. M. Glazov ◽

E. L. Ivchenko

Keyword(s):

Transition Metal ◽

Band Structure ◽

Second Harmonic ◽

Polarized Light ◽

Charge Carriers ◽

Photon Absorption ◽

Transition Metal Dichalcogenide ◽

Optical Orientation ◽

Circularly Polarized Light ◽

Valley Polarization

The main aspects of physical phenomena associated with the optical orientation of the spin and valley degrees of freedom in transition metal dichalcogenide monolayers and in van der Waals heterostructures based on them have been briefly reviewed. Owing to features of the band structure and spin–orbit coupling in such systems, circularly polarized light induces optical transitions in different valleys K+ and K– of the Brillouin zone; consequently, the optical orientation of charge carriers and excitons is accompanied by their valley polarization. The main features of the band structure of transition metal dichalcogenide monolayers, excitonic effects, and results of theoretical studies of the valley orientation of excitons and electrons at one-photon absorption have been reported. The linear–circular dichroism and valley orientation of free charge carriers and excitons at multiphoton absorption have been studied. Effects associated with the trigonal symmetry of monolayers, including the inversion of valley polarization at two-photon transitions and the second harmonic generation, have been discussed. The considered theoretical models have been illustrated by experimental data.

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Room-Temperature Valley Polarization and Coherence in Transition Metal Dichalcogenide–Graphene van der Waals Heterostructures

ACS Photonics ◽

10.1021/acsphotonics.8b01306 ◽

2018 ◽

Vol 5 (12) ◽

pp. 5047-5054 ◽

Cited By ~ 11

Author(s):

Etienne Lorchat ◽

Stefano Azzini ◽

Thibault Chervy ◽

Takashi Taniguchi ◽

Kenji Watanabe ◽

...

Keyword(s):

Transition Metal ◽

Room Temperature ◽

Van Der Waals ◽

Transition Metal Dichalcogenide ◽

Van Der Waals Heterostructures ◽

Valley Polarization

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Valley Polarization and Valleyresistance in a Monolayer Transition Metal Dichalcogenide Superlattice

The Journal of Physical Chemistry Letters ◽

10.1021/acs.jpclett.0c00863 ◽

2020 ◽

Vol 11 (10) ◽

pp. 3882-3888

Author(s):

Hui-Ying Mu ◽

Yi-Tong Yao ◽

Jie-Ru Li ◽

Guo-Cai Liu ◽

Chao He ◽

...

Keyword(s):

Transition Metal ◽

Transition Metal Dichalcogenide ◽

Valley Polarization

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Layer-engineered interlayer excitons

Science Advances ◽

10.1126/sciadv.abh0863 ◽

2021 ◽

Vol 7 (30) ◽

pp. eabh0863

Author(s):

Qinghai Tan ◽

Abdullah Rasmita ◽

Si Li ◽

Sheng Liu ◽

Zumeng Huang ◽

...

Keyword(s):

Transition Metal ◽

Band Structure ◽

Optoelectronic Property ◽

Transition Metal Dichalcogenide ◽

Two Dimensional ◽

Multilayer Heterostructures ◽

Valley Polarization ◽

Band Transition ◽

The Way

Photoluminescence (PL) from excitons serves as a powerful tool to characterize the optoelectronic property and band structure of semiconductors, especially for atomically thin two-dimensional transition metal dichalcogenide (TMD) materials. However, PL quenches quickly when the thickness of TMD materials increases from monolayer to a few layers, due to the change from direct to indirect band transition. Here, we show that PL can be recovered by engineering multilayer heterostructures, with the band transition reserved to be a direct type. We report emission from layer-engineered interlayer excitons from these multilayer heterostructures. Moreover, as desired for valleytronics devices, the lifetime, valley polarization, and valley lifetime of the generated interlayer excitons can all be substantially improved as compared with that in the monolayer-monolayer heterostructure. Our results pave the way for controlling the properties of interlayer excitons by layer engineering.

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Full-zone valley polarization landscape of finite-momentum exciton in transition metal dichalcogenide monolayers

Physical Review Research ◽

10.1103/physrevresearch.3.043198 ◽

2021 ◽

Vol 3 (4) ◽

Author(s):

Ping-Yuan Lo ◽

Guan-Hao Peng ◽

Wei-Hua Li ◽

Yi Yang ◽

Shun-Jen Cheng

Keyword(s):

Transition Metal ◽

Transition Metal Dichalcogenide ◽

Valley Polarization

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Optical properties of uniaxially strained graphene on transition metal dichalcogenide substrate

International Journal of Modern Physics B ◽

10.1142/s0217979218501643 ◽

2018 ◽

Vol 32 (13) ◽

pp. 1850164 ◽

Cited By ~ 1

Author(s):

Partha Goswami

Keyword(s):

Transition Metal ◽

Strain Field ◽

Graphene Monolayer ◽

Transition Metal Dichalcogenide ◽

Field Frequency ◽

Long Wavelength ◽

Strained Graphene ◽

Valley Polarization ◽

Doped Graphene ◽

Spin Degeneracy

The uniaxially strained graphene monolayer on transition metal dichalcogenide (GrTMD) substrate, constituting a van der Waals heterostructure (vdWH), is found to possess unusual intra-band plasmon dispersion ([Formula: see text]) with stronger incarceration compared to that of a standalone, doped graphene for finite doping in the long wavelength limit. The intra-band absorbance of GrTMD is found to be an increasing (decreasing) function of the strain field (frequency) at a given frequency (strain field). It is also observed that whereas the strain field is responsible for the valley polarization, a Rashba coupling-dependent pseudo Zeeman term arising due to the interplay of substrate-induced interactions is found to bring about the spin degeneracy lifting and the gate voltage tunable spin polarization. The latter turns out to be inversely proportional to the square root of the carrier concentration.

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