Electrically tunable valley polarization and valley coherence in monolayer WSe <sub>2</sub> embedded in a van der Waals heterostructure

Chakraborty, Chitraleema; Mukherjee, Arunabh; Qiu, Liangyu; Vamivakas, A. Nick

doi:10.1364/ome.9.001479

Cited by 25 publications

(24 citation statements)

References 41 publications

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“…As mentioned earlier, TMDCs can exhibit valley and spin selective interaction with light. WSe 2 is one such example which has spin-polarized valleys [137][138][139][140]. For example, all the electrons in the K-valley are spin-up and in the K'-valley are spin-down in ML WSe 2 .…”

Section: Light Emitting Devicesmentioning

confidence: 99%

Optoelectronic and photonic devices based on transition metal dichalcogenides

Thakar

Lodha

2020

Mater. Res. Express

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Transition metal dichalcogenides (TMDCs) are a family of two-dimensional layered materials (2DLMs) with extraordinary optical properties. They present an attractive option for future multifunctional and high-performance optoelectronics. However, much remains to be done to realize a mature technology for commercial applications. In this review article, we describe the progress and scope of TMDC devices in optical and photonic applications. Various photoresponse mechanisms observed in such devices and a brief discussion on measurement and analysis methods are described. Three main types of optoelectronic devices, namely photodetectors, photovoltaics and lightemitting devices are discussed in detail with a focus on device architecture and operation. Examples showing experimental integration of 2DLM-based devices with silicon photonics are also discussed briefly. A wide range of data for key performance metrics is analysed with insights into future directions for device design, processing and characterization that can help overcome present gaps and challenges. While the field is still in its infancy and requires significant efforts toward standardizing various approaches towards a mature technology, it has already shown promising results in broader aspects of compatibility, integration and performance for future electronics. Sensors are increasingly becoming an integrated part of the global electronic eco-system with the rise of data-driven technologies. There is a growing need for networks of cost-effective, robust and reliable sensors and their integration with present technologies. Optoelectronic and photonic devices are of importance for both sensing as well as high-speed optical communication applications. 2DLMs demonstrate significant light-matter interaction that is tunable with external physical and electronic parameters such as pressure, strain, electric and magnetic field [1-6]. Moreover, 2DLMs show strong dependence of their band structure on thickness with a transition to direct bandgap in monolayers in most of the known 2DLMs [7][8][9]. Graphene has been the most studied material since its discovery in 2004 [10][11][12]. Apart from graphene, there are nearly 1500 possible 2DLMs with a wide range of material properties as predicted by first principle simulations [13]. Transition metal dichalcogenides (TMDCs) are a family of 2DLMs in the form of MX 2 compounds, where M is a transition metal (Mo, W, Re) and X is a chalcogen (S, Se, Te). TMDCs are promising for electronic applications due to their semiconducting behaviour as opposed to semi-metallic graphene, and better thermal stability than materials such as black phosphorus and silicene [14][15][16][17][18][19]. Optoelectronic devices based on TMDCsTMDCs have been the most studied 2DLMs, apart from graphene and black phosphorus, for electronic and optoelectronic device applications [20,21]. They have a sizeable bandgap in the visible and near infrared (NIR) range (∼1-2 eV) that is optimal for optoelectronic sensors and light-emitting sources for short-ran...

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Section: Light Emitting Devicesmentioning

confidence: 99%

Optoelectronic and photonic devices based on transition metal dichalcogenides

Thakar

Lodha

2020

Mater. Res. Express

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“…At low current densities and low temperatures (~5 K), spectrally narrow lines were observed in the electroluminescence from spatially localized regions in the monolayer semiconductor. van der Waals heterostructure-based devices were also used to demonstrate the quantum-confined Stark effect in both localized [113,115,120] and delocalized excitons [121][122][123] in 2D materials. Both quadratic and linear Stark effects were observed from quantum emitters with a maximum energy control of ~21 meV.…”

Section: Quantum Light Manipulationmentioning

confidence: 99%

Advances in quantum light emission from 2D materials

2019

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Two-dimensional (2D) materials are being actively researched due to their exotic electronic and optical properties, including a layer-dependent bandgap, a strong exciton binding energy, and a direct optical access to electron valley index in momentum space. Recently, it was discovered that 2D materials with bandgaps could host quantum emitters with exceptional brightness, spectral tunability, and, in some cases, also spin properties. This review considers the recent progress in the experimental and theoretical understanding of these localized defect-like emitters in a variety of 2D materials as well as the future advantages and challenges on the path toward practical applications.

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“…The valley decoherence rate differs from the valley depolarization rate by its additional sensitivity to pure dephasing ( γ dep ). This results in a different expression

63 , 64 . Unique temperature dependencies for ρ VP and ρ VC are therefore expected and observed in Fig.…”

Section: Resultsmentioning

confidence: 99%

Valley phenomena in the candidate phase change material WSe2(1-x)Te2x

et al. 2020

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Alloyed transition metal dichalcogenides provide a unique opportunity for coupling band engineering and valleytronic phenomena in an atomically-thin platform. However, valley properties in alloys remain largely unexplored. We investigate the valley degree of freedom in monolayer alloys of the phase change candidate material WSe2(1-x)Te2x. Low temperature Raman measurements track the alloy-induced transition from the semiconducting 1H phase of WSe2 to the semimetallic 1Td phase of WTe2. We correlate these observations with density functional theory calculations and identify new Raman modes from 1H-WTe2. Photoluminescence measurements show ultra-low energy emission features that highlight the presence of significant alloy disorder arising from the large W-Te bond lengths. Interestingly, valley polarization and coherence in alloys survive at high Te compositions and are more robust against temperature than in WSe2. These findings illustrate the persistence of valley properties in alloys with highly dissimilar parent compounds and suggest band engineering can be utilized for valleytronic devices.

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Electrically tunable valley polarization and valley coherence in monolayer WSe ₂ embedded in a van der Waals heterostructure

Cited by 25 publications

References 41 publications

Optoelectronic and photonic devices based on transition metal dichalcogenides

Optoelectronic and photonic devices based on transition metal dichalcogenides

Advances in quantum light emission from 2D materials

Valley phenomena in the candidate phase change material WSe2(1-x)Te2x

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Electrically tunable valley polarization and valley coherence in monolayer WSe 2 embedded in a van der Waals heterostructure

Cited by 25 publications

References 41 publications

Optoelectronic and photonic devices based on transition metal dichalcogenides

Optoelectronic and photonic devices based on transition metal dichalcogenides

Advances in quantum light emission from 2D materials

Valley phenomena in the candidate phase change material WSe2(1-x)Te2x

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Electrically tunable valley polarization and valley coherence in monolayer WSe ₂ embedded in a van der Waals heterostructure