Magnetic-Field-Induced Rotation of Polarized Light Emission from Monolayer<mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" display="inline"><mml:msub><mml:mi>WS</mml:mi><mml:mn>2</mml:mn></mml:msub></mml:math>

Schmidt, Robert; Arora, Ashish; Plechinger, Gerd; Nagler, Philipp; Águila, Andrés Granados del; Ballottin, Mariana V.; Christianen, Peter C. M.; Vasconcellos, Steffen Michaelis de; Schüller, Christian; Korn, Tobias; Bratschitsch, Rudolf

doi:10.1103/physrevlett.117.077402

Cited by 89 publications

(100 citation statements)

References 44 publications

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“…A second cause for the decrease in the detected linear polarization can be dephasing induced during the PL lifetime [79]. Note that a smaller rotation angle of the PL with respect to the one observed in WSe 2 [50] and WS 2 [49] MLs (characterized by larger g factors) is indeed expected for a smaller exciton g factor measured in our sample.…”

Section: Rotation Of Valley Coherencementioning

confidence: 74%

“…Generation of valley coherence is achieved optically by linearly polarized excitation σ X , which results in strongly linearly polarized neutral exciton (X 0 ) emission [26]. Recent experiments have shown that this valley polarization can be rotated in ML WSe 2 and WS 2 [49][50][51], a first important step towards full control of valley states [87]. The MoS 2 ML is excited by a linearly polarized (σ X ) continuous wave He-Ne laser (1.96 eV) to generate valley coherence (i.e., optical alignment of excitons [80]).…”

Section: Rotation Of Valley Coherencementioning

confidence: 99%

“…Here, we discuss the possible impact of doping (i.e., contributions from charged excitons) and the dielectric environment. We also show the generation and rotation of robust valley coherence, a coherent superposition of valley states using the chiral optical selection rules [26], an important step towards full optical control of valley states in these 2D materials [49][50][51].…”

Section: Introductionmentioning

confidence: 99%

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Excitonic Linewidth Approaching the Homogeneous Limit in MoS2 -Based van der Waals Heterostructures

et al. 2017

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The strong light-matter interaction and the valley selective optical selection rules make monolayer (ML) MoS 2 an exciting 2D material for fundamental physics and optoelectronics applications. But, so far, optical transition linewidths even at low temperature are typically as large as a few tens of meV and contain homogeneous and inhomogeneous contributions. This prevented in-depth studies, in contrast to the bettercharacterized ML materials MoSe 2 and WSe 2 . In this work, we show that encapsulation of ML MoS 2 in hexagonal boron nitride can efficiently suppress the inhomogeneous contribution to the exciton linewidth, as we measure in photoluminescence and reflectivity a FWHM down to 2 meV at T ¼ 4 K. Narrow optical transition linewidths are also observed in encapsulated WS 2 , WSe 2 , and MoSe 2 MLs. This indicates that surface protection and substrate flatness are key ingredients for obtaining stable, high-quality samples. Among the new possibilities offered by the well-defined optical transitions, we measure the homogeneous broadening induced by the interaction with phonons in temperature-dependent experiments. We uncover new information on spin and valley physics and present the rotation of valley coherence in applied magnetic fields perpendicular to the ML.

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Section: Rotation Of Valley Coherencementioning

confidence: 74%

Section: Rotation Of Valley Coherencementioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

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Excitonic Linewidth Approaching the Homogeneous Limit in MoS2 -Based van der Waals Heterostructures

et al. 2017

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“…Note added in proof : After submission of our manuscript, results demonstrating the rotation of the valley pseudospin by static magnetic fields were reported by other researchers 35,36 .…”

mentioning

confidence: 95%

Optical manipulation of valley pseudospin

Ye¹,

Sun²,

Heinz³

2016

Nature Phys

235

223

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The coherent manipulation of spin and pseudospin underlies existing and emerging quantum technologies, including quantum communication and quantum computation 1,2 . Valley polarization, associated with the occupancy of degenerate, but quantum mechanically distinct valleys in momentum space, closely resembles spin polarization and has been proposed as a pseudospin carrier for the future quantum electronics 3,4 . Valley exciton polarization has been created in the transition metal dichalcogenide monolayers using excitation by circularly polarized light and has been detected both optically 5-7 and electrically 8 . In addition, the existence of coherence in the valley pseudospin has been identified experimentally 9 . The manipulation of such valley coherence has, however, remained out of reach. Here we demonstrate all-optical control of the valley coherence by means of the pseudomagnetic field associated with the optical Stark e ect. Using below-bandgap circularly polarized light, we rotate the valley exciton pseudospin in monolayer WSe 2 on the femtosecond timescale. Both the direction and speed of the rotation can be manipulated optically by tuning the dynamic phase of excitons in opposite valleys. This study unveils the possibility of generation, manipulation, and detection of the valley pseudospin by coupling to photons.The broken inversion symmetry in monolayer transition metal dichalcogenide (TMDC) crystals in the semiconducting MX 2 (M = Mo, W; X = S, Se) family gives rise to a nontrivial Berry phase at the K and K valleys in momentum space 10 , where the optically accessible direct bandgap occurs in these materials 11,12 . This Berry phase, together with the angular momentum of the atomic orbitals, leads to different optical selection rules for the two valleys: excitons in the K valley couple to left-circularly polarized photons, while excitons in the K valley couple to right-circularly polarized photons, thus permitting the optical generation of valley polarization through control of the helicity of light [5][6][7] . Moreover, when a TMDC monolayer is excited with linearly polarized light, a coherent superposition state is established between the K and K valley excitons 9 . Such a coherent state can, in principle, be manipulated by lifting the energy degeneracy between valleys through the breaking of time-reversal symmetry in the material. In this regard, d.c. magnetic fields have been applied to achieve a valley splitting of a few meV [13][14][15][16] . Circularly polarized light also breaks time-reversal symmetry, and researchers have used it to create larger valley splittings, corresponding to pseudomagnetic fields up to 60 T (refs 17,18). In addition, this optical approach permits us to access the ultrafast timescale: in this work, we demonstrate the coherent manipulation of the valley pseudospin on the femtosecond timescale.The optical Stark effect has been applied to manipulate the spin/pseudospin in quantum systems, such as atomic quantum gases 19 , quantum dots 20,21 , and III-V quantum wells 22 . H...

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“…Broken spatial inversion symmetry and strong spin-orbit interactions introduce valley-contrasting physical properties that enable manipulation of the valley pseudospin degree of freedom (DoF) [1–7]. Most notably, electrons and holes residing at the K and K ′ valleys possess opposite spin, orbital magnetic moment, and Berry curvature [8].…”

Section: Introductionmentioning

confidence: 99%

Trion valley coherence in monolayer semiconductors

Hao

et al. 2017

2D Mater.

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The emerging field of valleytronics aims to exploit the valley pseudospin of electrons residing near Bloch band extrema as an information carrier. Recent experiments demonstrating optical generation and manipulation of exciton valley coherence (the superposition of electron-hole pairs at opposite valleys) in monolayer transition metal dichalcogenides (TMDs) provide a critical step towards control of this quantum degree of freedom. The charged exciton (trion) in TMDs is an intriguing alternative to the neutral exciton for control of valley pseudospin because of its long spontaneous recombination lifetime, its robust valley polarization, and its coupling to residual electronic spin. Trion valley coherence has however been unexplored due to experimental challenges in accessing it spectroscopically. In this work, we employ ultrafast two-dimensional coherent spectroscopy to resonantly generate and detect trion valley coherence in monolayer MoSe2 demonstrating that it persists for a few-hundred femtoseconds. We conclude that the underlying mechanisms limiting trion valley coherence are fundamentally different from those applicable to exciton valley coherence.

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Magnetic-Field-Induced Rotation of Polarized Light Emission from MonolayerWS2

Cited by 89 publications

References 44 publications

Excitonic Linewidth Approaching the Homogeneous Limit in MoS2 -Based van der Waals Heterostructures

Excitonic Linewidth Approaching the Homogeneous Limit in MoS2 -Based van der Waals Heterostructures

Optical manipulation of valley pseudospin

Trion valley coherence in monolayer semiconductors

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