scholarly journals Valley-Selective Response of Nanostructures Coupled to 2D Transition-Metal Dichalcogenides

2018 ◽  
Vol 8 (7) ◽  
pp. 1157 ◽  
Author(s):  
Alexander Krasnok ◽  
Andrea Alù
Keyword(s):  
Transition Metal ◽  
Room Temperature ◽  
State Of The Art ◽  
Transition Metal Dichalcogenides ◽  
Zone Boundary ◽  
Brillouin Zone Boundary ◽  
Directional Emission ◽  
Metal Dichalcogenides ◽  
On Chip ◽  
Valley Hall Effect

Monolayer (1L) transition-metal dichalcogenides (TMDCs) are attractive materials for several optoelectronic applications because of their strong excitonic resonances and valley-selective response. Valley excitons in 1L-TMDCs are formed at opposite points of the Brillouin zone boundary, giving rise to a valley degree of freedom that can be treated as a pseudospin, and may be used as a platform for information transport and processing. However, short valley depolarization times and relatively short exciton lifetimes at room temperature prevent using valley pseudospins in on-chip integrated valley devices. Recently, it was demonstrated how coupling these materials to optical nanoantennas and metasurfaces can overcome this obstacle. Here, we review the state-of-the-art advances in valley-selective directional emission and exciton sorting in 1L-TMDC mediated by nanostructures and nanoantennas. We briefly discuss the optical properties of 1L-TMDCs paying special attention to their photoluminescence/absorption spectra, dynamics of valley depolarization, and the valley Hall effect. Then, we review recent works on nanostructures for valley-selective directional emission from 1L-TMDCs.

scholarly journals Microscopic Origin of the Valley Hall Effect in Transition Metal Dichalcogenides Revealed by Wavelength-Dependent Mapping

Nano Letters ◽  
2017 ◽  
Vol 17 (9) ◽  
pp. 5719-5725 ◽  
Author(s):  
Nicolas Ubrig ◽  
Sanghyun Jo ◽  
Marc Philippi ◽  
Davide Costanzo ◽  
Helmuth Berger ◽  
...  
Keyword(s):  
Transition Metal ◽  
Hall Effect ◽  
Transition Metal Dichalcogenides ◽  
Metal Dichalcogenides ◽  
Valley Hall Effect ◽  
Microscopic Origin

scholarly journals Intrinsic lifetime of higher excitonic states in tungsten diselenide monolayers

Nanoscale ◽  
2019 ◽  
Vol 11 (25) ◽  
pp. 12381-12387 ◽  
Author(s):  
Samuel Brem ◽  
Jonas Zipfel ◽  
Malte Selig ◽  
Archana Raja ◽  
Lutz Waldecker ◽  
...  
Keyword(s):  
Transition Metal ◽  
Room Temperature ◽  
Transition Metal Dichalcogenides ◽  
Optical Spectra ◽  
Tungsten Diselenide ◽  
Dielectric Screening ◽  
Metal Dichalcogenides ◽  
Excitonic States

The reduced dielectric screening in atomically thin transition metal dichalcogenides allows to study the hydrogen-like series of higher exciton states in optical spectra even at room temperature.

scholarly journals Giant optical anisotropy in transition metal dichalcogenides for next-generation photonics

2020 ◽  
Author(s):  
Georgy Ermolaev ◽  
D. Grudinin ◽  
Y. Stebunov ◽  
K. Voronin ◽  
Vasyl Kravets ◽  
...  
Keyword(s):  
Transition Metal ◽  
Optical Anisotropy ◽  
Near Infrared ◽  
Near Field ◽  
Transition Metal Dichalcogenides ◽  
Next Generation ◽  
Infrared Wavelength ◽  
Infrared Spectral ◽  
Metal Dichalcogenides ◽  
On Chip

Abstract Large optical anisotropy observed in a broad spectral range is of paramount importance for efficient light manipulation in countless devices. Although a giant anisotropy was recently observed in the mid-infrared wavelength range, for visible and near-infrared spectral intervals, the problem remains acute with the highest reported birefringence values of 0.8 in BaTiS3 and h-BN crystals. This inspired an intensive search for giant optical anisotropy among natural and artificial materials. Here, we demonstrate that layered transition metal dichalcogenides (TMDCs) provide an answer to this quest owing to their fundamental differences between intralayer strong covalent bonding and weak interlayer van der Walls interaction. To do this, we carried out a correlative far- and near-field characterization validated by first-principle calculations that reveals an unprecedented birefringence of 1.5 in the infrared and 3 in the visible light for MoS2. Our findings demonstrate that this outstanding anisotropy allows for tackling the diffraction limit enabling an avenue for on-chip next-generation photonics.

scholarly journals Room Temperature Terahertz Electroabsorption Modulation by Excitons in Monolayer Transition Metal Dichalcogenides

Nano Letters ◽  
2020 ◽  
Vol 20 (7) ◽  
pp. 5214-5220
Author(s):  
Jiaojian Shi ◽  
Edoardo Baldini ◽  
Simone Latini ◽  
Shunsuke A. Sato ◽  
Yaqing Zhang ◽  
...  
Keyword(s):  
Transition Metal ◽  
Room Temperature ◽  
Transition Metal Dichalcogenides ◽  
Metal Dichalcogenides

scholarly journals Giant optical anisotropy in transition metal dichalcogenides for next-generation photonics

2021 ◽  
Vol 12 (1) ◽  
Author(s):  
G. A. Ermolaev ◽  
D. V. Grudinin ◽  
Y. V. Stebunov ◽  
K. V. Voronin ◽  
V. G. Kravets ◽  
...  
Keyword(s):  
Transition Metal ◽  
Optical Anisotropy ◽  
Near Infrared ◽  
Near Field ◽  
Transition Metal Dichalcogenides ◽  
Next Generation ◽  
Infrared Wavelength ◽  
Infrared Spectral ◽  
Metal Dichalcogenides ◽  
On Chip

AbstractLarge optical anisotropy observed in a broad spectral range is of paramount importance for efficient light manipulation in countless devices. Although a giant anisotropy has been recently observed in the mid-infrared wavelength range, for visible and near-infrared spectral intervals, the problem remains acute with the highest reported birefringence values of 0.8 in BaTiS3 and h-BN crystals. This issue inspired an intensive search for giant optical anisotropy among natural and artificial materials. Here, we demonstrate that layered transition metal dichalcogenides (TMDCs) provide an answer to this quest owing to their fundamental differences between intralayer strong covalent bonding and weak interlayer van der Waals interaction. To do this, we made correlative far- and near-field characterizations validated by first-principle calculations that reveal a huge birefringence of 1.5 in the infrared and 3 in the visible light for MoS2. Our findings demonstrate that this remarkable anisotropy allows for tackling the diffraction limit enabling an avenue for on-chip next-generation photonics.

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.

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