Electric control of valley polarization in monolayer WSe2 using a van der Waals magnet

Li, Jiaxin; Li, Weiqing; Hung, Sheng-Hsiung; Chen, Po-Liang; Yang, Yaw Wen; Chang, Tian-Yun; Chiu, Po‐Wen; Jeng, Horng‐Tay; Liu, Chang Hua

doi:10.1038/s41565-022-01115-2

Cited by 44 publications

(49 citation statements)

References 42 publications

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“…In addition to reserving the extraordinary properties of each constituent 2DMs, vdW heterostructures exhibit new fascinating physical phenomena, such as valley polarization, valley Hall, and Zeeman effects and other valley‐contrasting related effects. [ 128 , 129 , 130 ] In addition, the atomic alignment of two 2DMs layer exhibits periodic variations that is defined as moiré superlattice. Accompanied with in‐plane superlattice, the as‐generated moiré interlayer excitons with specific optical selective rules become a versatile platform for exploring exciton‐ and valley‐related physics.…”

Section: Heterostructuresmentioning

confidence: 99%

The Interaction of 2D Materials With Circularly Polarized Light

et al. 2023

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2D materials (2DMs), due to spin‐valley locking degree of freedom, exhibit strongly bound exciton and chiral optical selection rules and become promising material candidates for optoelectronic and spin/valleytronic devices. Over the last decade, the manifesting of 2D materials by circularly polarized lights expedites tremendous fascinating phenomena, such as valley/exciton Hall effect, Moiré exciton, optical Stark effect, circular dichroism, circularly polarized photoluminescence, and spintronic property. In this review, recent advance in the interaction of circularly polarized light with 2D materials covering from graphene, black phosphorous, transition metal dichalcogenides, van der Waals heterostructures as well as small proportion of quasi‐2D perovskites and topological materials, is overviewed. The confronted challenges and theoretical and experimental opportunities are also discussed, attempting to accelerate the prosperity of chiral light‐2DMs interactions.

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Section: Heterostructuresmentioning

confidence: 99%

The Interaction of 2D Materials With Circularly Polarized Light

et al. 2023

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“…The degree of valley polarization is quantitatively evaluated according to the expression ρ ¼ ðI It should be noted that the obtained valley polarization in H∕T-WSe 2 is much larger than that of pure H-WSe 2 , 35 and the maximum value is record-high under the nonresonant excitation so far. 13,36,37 The magnetic field-dependent valley polarizations with σ − excitation are compared and depicted in Figs. 3(a for different T-phase concentrations.…”

Section: Characterization Of Valley Polarizationmentioning

confidence: 99%

“…12 Further, combining with the spin injection through a magnetic heterojunction or ferromagnetic electrode, the magnitude of a required magnetic field can be reduced by taking advantage of the injected nonequilibrium spin carriers. [13][14][15] Nevertheless, the complicated growth process and specially designed structures result in the lattice mismatch and poor integrability of devices. Meanwhile, the clean interface and conductivity matching are indispensable for efficient spin injection, which are difficult to control precisely in the magnetic heterojunction.…”

Section: Introductionmentioning

confidence: 99%

Controllable valley magnetic response in phase-transformed tungsten diselenide

Liu

Zhang

et al. 2023

Adv. Photon. Nexus

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Achieving valley pseudospin with large polarization is crucial in the implementation of quantum information applications. Transition metal dichalcogenides (TMDC) with different phase structures provide an ideal platform for valley modulation. The valley splitting has been achieved in hybrid phase WSe 2 , while its valley polarization remains unstudied. Magnetic field controllable valley polarization is explored in WSe 2 with coexistence of H and T phases by an all-optical route. A record high valley polarization of 58.3% is acquired with a 19.9% T phase concentration under a 4-T magnetic field and nonresonant excitation. The enhanced valley polarization is dependent on the phase component and shows various increasing slopes, owing to the synergy between the T phase WSe 2 and the magnetic field. The magnetic field controlled local magnetic momentums are revealed as the mechanism for the large valley polarization in H∕T-WSe 2 . This speculation is also verified by theoretical simulations of the nonequilibrium spin density. These results display a considerable valley magnetic response in phase-engineered TMDC and provide a large-scale scheme for valley polarization applications.

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“…As a proof of concept, the WSe 2 -plasmonic chiral metasurface hybrid was shown to display nearly reversible ON/OFF switching of the valley-polarized emission in water and in air under cyclic experiments. [171] Second, previous methods for controlling the valley-polarized emission of a single layer of transition metal dichalcogenide include the application of an electrical bias and optical pumping; [174,175] however, both approaches rely on carrier injection to create disproportionate valley populations. The employment of chiral metasurfaces proposed by Wu et al is solely based on chiral-selective light-matter interactions.…”

Section: Wwwadvmatde Wwwadvancedsciencenewscommentioning

confidence: 99%

Recent Advances in Ultrathin Chiral Metasurfaces by Twisted Stacking

et al. 2022

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chiral plasmonic nanoparticles and their self-assembled structures as colloidal suspensions. [6][7][8][9] Recently, beyond noble metal plasmonics, solid-state layered nanomaterials that are rotationally aligned with a defined twist angle are becoming increasingly investigated (Figure 1). Among these are twisted 2D van der Waals (vdW) materials, [10][11][12] twisted single-crystal slabs, [13,14] twisted aligned nanowire thin films, [15][16][17][18] and twisted metasurfaces with periodic subunits [19][20][21] (Figure 2). These chiral stacked materials possessing geometric handedness and optical chirality can be seen as truncated and minimalistic versions of supramolecular liquid crystals in the chiral nematic phase or of 3D chiral photonic crystals. [22][23][24] Compared to their bulk or multiple-layer counterparts, the fabrication becomes greatly simplified for bilayer or few-layer chiral metamaterials, enabling precise control over the interlayer twist angle to manipulate lightmatter interactions. Ultrathin chiral metamaterials and metasurfaces with tunable optical and chiroptical responses are thus an active field for study.Twisting achiral layered nanostructures in parallel planes enables engineering of the extrinsic chirality and related optical performance. Specifically, the twist angle from counterclockwise rotation of an upper layer with respect to the beneath one is defined to be positive, θ > 0°, leading to a left-handed stacking geometry. [10,18] Accordingly, negative twist angle from clockwise rotation gives rise to the right-handed counterpart. Accurate control over the interlayer rotation angle offers flexible manipulation of properties, especially optical activity, of twisted layered systems of a wide variety of monolayer constituents and dimensions. A well-studied system is twisted bilayer graphene (TBG), catalyzing the research on twisted stacked nanostructures over the past few years, especially as many intriguing properties of magic-angle graphene are uncovered. [28][29][30] The twist angle dependencies of phonon dispersion, [31] optical absorption and reflection, [32,33] circular dichroism (CD) and birefringence, [10,34] second harmonic generation (SHG), [35] and photoresponse [36,37] of TBG have been extensively explored in the past few years. Similar realizations have been reported for twisted nanostructures of other 2D materials such as transition metal dichalcogenides, [38,39] graphitic carbon nitride, [40] and hexagonal boron nitride (hBN), [41] as well as non-2D systems like polymeric thin films or patterned plasmonic nanohole arrays. [42,43] Therefore, there exists fertile ground for chiral metasurface design Artificial chiral nanostructures have been subjected to extensive research for their unique chiroptical activities. Planarized chiral films of ultrathin thicknesses are in particular demand for easy on-chip integration and improved energy efficiency as polarization-sensitive metadevices. Recently, controlled twisted stacking of two or more layers of nanomaterials, such as 2D van der ...

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Electric control of valley polarization in monolayer WSe2 using a van der Waals magnet

Cited by 44 publications

References 42 publications

The Interaction of 2D Materials With Circularly Polarized Light

The Interaction of 2D Materials With Circularly Polarized Light

Controllable valley magnetic response in phase-transformed tungsten diselenide

Recent Advances in Ultrathin Chiral Metasurfaces by Twisted Stacking

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