Valley Polarization in Transition-Metal Dichalcogenides by Optical Pumping

2013 ◽  
pp. 269-287
Author(s):  
Junfeng Dai ◽  
Xiaodong Cui
Keyword(s):  
Transition Metal ◽  
Optical Pumping ◽  
Transition Metal Dichalcogenides ◽  
Valley Polarization ◽  
Metal Dichalcogenides

scholarly journals Optically initialized robust valley-polarized holes in monolayer WSe2

2015 ◽  
Vol 6 (1) ◽  
Author(s):  
Wei-Ting Hsu ◽  
Yen-Lun Chen ◽  
Chang-Hsiao Chen ◽  
Pang-Shiuan Liu ◽  
Tuo-Hung Hou ◽  
...  
Keyword(s):  
Transition Metal ◽  
Low Temperatures ◽  
Room Temperature ◽  
Optical Pumping ◽  
Transition Metal Dichalcogenides ◽  
Kerr Rotation ◽  
Time Resolved ◽  
Recombination Lifetime ◽  
Valley Polarization ◽  
Metal Dichalcogenides

Abstract A robust valley polarization is a key prerequisite for exploiting valley pseudospin to carry information in next-generation electronics and optoelectronics. Although monolayer transition metal dichalcogenides with inherent spin–valley coupling offer a unique platform to develop such valleytronic devices, the anticipated long-lived valley pseudospin has not been observed yet. Here we demonstrate that robust valley-polarized holes in monolayer WSe2 can be initialized by optical pumping. Using time-resolved Kerr rotation spectroscopy, we observe a long-lived valley polarization for positive trion with a lifetime approaching 1 ns at low temperatures, which is much longer than the trion recombination lifetime (∼10–20 ps). The long-lived valley polarization arises from the transfer of valley pseudospin from photocarriers to resident holes in a specific valley. The optically initialized valley pseudospin of holes remains robust even at room temperature, which opens up the possibility to realize room-temperature valleytronics based on transition metal dichalcogenides.

scholarly journals Valley-selective directional emission from a transition-metal dichalcogenide monolayer mediated by a plasmonic nanoantenna

2018 ◽  
Vol 9 ◽  
pp. 780-788 ◽  
Author(s):  
Haitao Chen ◽  
Mingkai Liu ◽  
Lei Xu ◽  
Dragomir N Neshev
Keyword(s):  
Transition Metal ◽  
Transition Metal Dichalcogenides ◽  
Information Storage ◽  
Transition Metal Dichalcogenide ◽  
Point Dipole ◽  
Antenna Structure ◽  
Direct Emission ◽  
Valley Polarization ◽  
Potential Applications ◽  
Metal Dichalcogenides

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.

scholarly journals Dark excitons and the elusive valley polarization in transition metal dichalcogenides

2D Materials ◽  
2017 ◽  
Vol 4 (2) ◽  
pp. 025016 ◽  
Author(s):  
M Baranowski ◽  
A Surrente ◽  
D K Maude ◽  
M Ballottin ◽  
A A Mitioglu ◽  
...  
Keyword(s):  
Transition Metal ◽  
Transition Metal Dichalcogenides ◽  
Valley Polarization ◽  
Metal Dichalcogenides

scholarly journals Inverted valley polarization in optically excited transition metal dichalcogenides

2018 ◽  
Vol 9 (1) ◽  
Author(s):  
Gunnar Berghäuser ◽  
Ivan Bernal-Villamil ◽  
Robert Schmidt ◽  
Robert Schneider ◽  
Iris Niehues ◽  
...  
Keyword(s):  
Transition Metal ◽  
Transition Metal Dichalcogenides ◽  
Valley Polarization ◽  
Metal Dichalcogenides ◽  
Excited Transition

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

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.

scholarly journals Deep subwavelength control of valley polarized cathodoluminescence in h-BN/WSe2/h-BN heterostructure

2021 ◽  
Vol 12 (1) ◽  
Author(s):  
Liheng Zheng ◽  
Zhixin Liu ◽  
Donglin Liu ◽  
Xingguo Wang ◽  
Yu Li ◽  
...  
Keyword(s):  
Information Technologies ◽  
Optical Pumping ◽  
Near Field ◽  
Transition Metal Dichalcogenides ◽  
Hybrid Structure ◽  
Effective Control ◽  
Polarization Degree ◽  
Valley Polarization ◽  
Metal Dichalcogenides ◽  
Field Excitation

AbstractValley pseudospin in transition metal dichalcogenides monolayers intrinsically provides additional possibility to control valley carriers, raising a great impact on valleytronics in following years. The spin-valley locking directly contributes to optical selection rules which allow for valley-dependent addressability of excitons by helical optical pumping. As a binary photonic addressable route, manipulation of valley polarization states is indispensable while effective control methods at deep-subwavelength scale are still limited. Here, we report the excitation and control of valley polarization in h-BN/WSe2/h-BN and Au nanoantenna hybrid structure by electron beam. Near-field circularly polarized dipole modes can be excited via precise stimulation and generate the valley polarized cathodoluminescence via near-field interaction. Effective manipulation of valley polarization degree can be realized by variation of excitation position. This report provides a near-field excitation methodology of valley polarization, which offers exciting opportunities for deep-subwavelength valleytronics investigation, optoelectronic circuits integration and future quantum information technologies.

scholarly journals Optical properties of atomically thin transition metal dichalcogenides: observations and puzzles

Nanophotonics ◽  
2017 ◽  
Vol 6 (6) ◽  
pp. 1289-1308 ◽  
Author(s):  
Maciej Koperski ◽  
Maciej R. Molas ◽  
Ashish Arora ◽  
Karol Nogajewski ◽  
Artur O. Slobodeniuk ◽  
...  
Keyword(s):  
Optical Properties ◽  
Transition Metal ◽  
Optical Pumping ◽  
Single Photon ◽  
Hexagonal Boron Nitride ◽  
Transition Metal Dichalcogenides ◽  
Wide Band ◽  
Open Questions ◽  
Single Photon Emitters ◽  
Metal Dichalcogenides

AbstractRecent results on the optical properties of monolayer and few layers of semiconducting transition metal dichalcogenides are reviewed. Experimental observations are presented and discussed in the frame of existing models, highlighting the limits of our understanding in this emerging field of research. We first introduce the representative band structure of these systems and their interband optical transitions. The effect of an external magnetic field is then considered to discuss Zeeman spectroscopy and optical pumping experiments, both revealing phenomena related to the valley degree of freedom. Finally, we discuss the observation of single photon emitters in different types of layered materials, including wide band gap hexagonal boron nitride. While going through these topics, we try to focus on open questions and on experimental observations, which do not yet have a clear explanation.

scholarly journals All-optical nonreciprocity due to valley polarization pumping in transition metal dichalcogenides

2021 ◽  
Vol 12 (1) ◽  
Author(s):  
Sriram Guddala ◽  
Yuma Kawaguchi ◽  
Filipp Komissarenko ◽  
Svetlana Kiriushechkina ◽  
Anton Vakulenko ◽  
...  
Keyword(s):  
Transition Metal ◽  
Transition Metal Dichalcogenides ◽  
Vital Role ◽  
Practical Applications ◽  
Propagation Of Light ◽  
Intervalley Scattering ◽  
All Optical ◽  
Valley Polarization ◽  
Metal Dichalcogenides ◽  
Pass Through

AbstractNonreciprocity and nonreciprocal optical devices play a vital role in modern photonic technologies by enforcing one-way propagation of light. Here, we demonstrate an all-optical approach to nonreciprocity based on valley-selective response in transition metal dichalcogenides (TMDs). This approach overcomes the limitations of magnetic materials and it does not require an external magnetic field. We provide experimental evidence of photoinduced nonreciprocity in a monolayer WS2 pumped by circularly polarized (CP) light. Nonreciprocity stems from valley-selective exciton population, giving rise to nonlinear circular dichroism controlled by CP pump fields. Our experimental results reveal a significant effect even at room temperature, despite considerable intervalley-scattering, showing promising potential for practical applications in magnetic-free nonreciprocal platforms. As an example, here we propose a device scheme to realize an optical isolator based on a pass-through silicon nitride (SiN) ring resonator integrating the optically biased TMD monolayer.

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