Optical control of room-temperature valley polaritons

Sun, Zheng; Gu, Jie; Ghazaryan, Areg; Shotan, Zav; Considine, Christopher R.; Dollar, Michael; Chakraborty, Biswanath; Liu, Xiaoze; Ghaemi, Pouyan; Kéna‐Cohen, Stéphane; Menon, Vinod M.

doi:10.1038/nphoton.2017.121

Cited by 188 publications

(204 citation statements)

References 35 publications

Supporting

Mentioning

197

Contrasting

Order By: Relevance

“…Furthermore, based on our discovery of carrier screening effect, chemical doping or heterostructure formation are also expected to affect the valley polarization of A excitons in TMDs, which is promising for nondegenerated P c engineering. Such enhanced polarization degree could provide additional degrees of freedom in realizing valley polarized exciton condensation, exciton–polariton emission and polariton fluid transport . Our studies develop a simple but practical strategy for electrical and optical control of the valley polarization state, which is a corner stone for future noncryogenic valleytronic operations.…”

mentioning

confidence: 92%

Engineering Valley Polarization of Monolayer WS₂: A Physical Doping Approach

Feng

Cong

Konabe

et al. 2019

Small

View full text Add to dashboard Cite

The emerging field of valleytronics has boosted intensive interests in investigating and controlling valley polarized light emission of monolayer transition metal dichalcogenides (1L TMDs). However, so far, the effective control of valley polarization degree in monolayer TMDs semiconductors is mostly achieved at liquid helium cryogenic temperature (4.2 K), with the requirements of high magnetic field and on‐resonance laser, which are of high cost and unwelcome for applications. To overcome this obstacle, it is depicted that by electrostatic and optical doping, even at temperatures far above liquid helium cryogenic temperature (80 K) and under off‐resonance laser excitation, a competitive valley polarization degree of monolayer WS2 can be achieved (more than threefold enhancement). The enhanced polarization is understood by a general doping dependent valley relaxation mechanism, which agrees well with the unified theory of carrier screening effects on intervalley scattering process. These results demonstrate that the tunability corresponds to an effective magnet field of ≈10 T at 4.2 K. This work not only serves as a reference to future valleytronic studies based on monolayer TMDs with various external or native carrier densities, but also provides an alternative approach toward enhanced polarization degree, which denotes an essential step toward practical valleytronic applications.

show abstract

mentioning

confidence: 92%

Engineering Valley Polarization of Monolayer WS₂: A Physical Doping Approach

Feng

Cong

Konabe

et al. 2019

Small

View full text Add to dashboard Cite

show abstract

“…For example, TMD planar waveguides could serve as F‐P microcavities due to their capability of confining photons within the waveguide . In addition, F‐P cavities based on metal mirrors were also used to create EPs in TMDs . In nearly all cases, the strong coupling between cavity photons and excitons is confirmed by the measurements of Rabi splitting energy Ω R , which is typically in the order of tens to hundreds of meV.…”

Section: Far‐field Spectroscopy Studies Of Eps In Tmdsmentioning

confidence: 99%

“…The general approach used in these studies is exciting the TMD sample with circularly polarized laser and then measuring the helicity (or percentage of polarization) of the emitted light due to EPs. The helicity can be defined as ρ = [ I (σ+) − I (σ−)]/[ I (σ+) + I (σ−)], where I (σ+) and I (σ−) are the intensities of emissions with left and right circular polarizations, respectively . An alternative approach for quantifying valley polarization is using the degree of linear polarization that is an indication of coherence between valleys …”

Section: Far‐field Spectroscopy Studies Of Eps In Tmdsmentioning

confidence: 99%

See 1 more Smart Citation

Recent Progress on Exciton Polaritons in Layered Transition‐Metal Dichalcogenides

Fei

2019

Advanced Optical Materials

View full text Add to dashboard Cite

Exciton polaritons (EPs) are half‐light, half‐matter quasiparticles formed due to the coupling between photons and excitons in semiconductors. Their uniqueness lies at the strong light–matter interactions and long‐distance transport, thus promising for many novel applications in photonics, information, and quantum technologies. Recently, EPs in group‐VI transition‐metal dichalcogenides (TMDs) have attracted a lot of research interest due to their room‐temperature stability, long‐distance propagation, and controllability through electric gating, valley‐selective optical pumping, and precise thickness control. In this progress report, recent studies of EPs in TMDs are reviewed, highlighting their key properties and functionalities, and then discussing the potential directions for future research.

show abstract

“…The valley information can then be characterized by substantial handedness in far-field photoluminescence (PL) due to the spin conservation during recombination of valley excitons. [17][18][19][20][21][22] Such valley-optical cavity hybrid systems exhibited room-temperature far-field PL of maintained handedness, which would benefit the application of valley degree of freedom. [9][10][11] However, the phonon-assisted intervalley scattering accelerates dramatically when temperature is increased, resulting in volatile valley states and significantly reduced handedness of far-field PL at room temperature.…”

mentioning

confidence: 99%

Room‐Temperature Active Modulation of Valley Dynamics in a Monolayer Semiconductor through Chiral Purcell Effects

Zhang

et al. 2019

Advanced Materials

View full text Add to dashboard Cite

of free-electron spins. Such valley pseudospins feature robust spin-valley locking and direct coupling to photon spins. [3,4] As a result, excitons in monolayer semiconductors possess additional valley degrees of freedom that are directly addressable through external means, making them promising carriers for information storage and processing in valleytronic devices. [1,2,5,6] Application of valley degree of freedom in optoelectronic devices requires the capability to access and manipulate the valley behaviors. The optical selection rule (i.e., selective coupling to photons with σ + and σ − circular polarization at K and K′ valleys, respectively) in monolayer semiconductors enables the direct addressing of a specific valley by excitation using circularly polarized lasers at cryogenic temperature. The valley information can then be characterized by substantial handedness in far-field photoluminescence (PL) due to the spin conservation during recombination of valley excitons. [7,8] The incorporation of monolayer semiconductors in optical cavities with polarization-dependent responses to an incident laser can further enhance the asymmetric excitation of valley excitons and the resulting PL handedness. [9][10][11] However, the phonon-assisted intervalley scattering accelerates dramatically when temperature is increased, resulting in volatile valley states and significantly reduced handedness of far-field PL at room temperature. [8,12,13] Recent efforts have shown that near-field couplings between optical cavities and valley spins are promising in solving the cryogenic-temperature limitation and enabling room-temperature control of valley dynamics. Specifically, spin-orbit couplings between valley-polarized exciton recombination and circularly polarized surface plasmons can spatially separate the valley spins into opposite inplane directions. [14][15][16] The formation of exciton-polaritons via strong coupling between valley excitons and optical cavities can also prevent the valley polarization from complete vanishing upon enhanced intervalley scattering. [17][18][19][20][21][22] Such valley-optical cavity hybrid systems exhibited room-temperature far-field PL of maintained handedness, which would benefit the application of valley degree of freedom. [19,22] However, modulation of valley behaviors at room temperature is still limited by the requirement of precise spatial and spectral overlap between excitons and optical cavities in current approaches. In addition, it remains unclear how to distinguish the effects of spindependent excitation and near-field-controlled relaxation on Spin-dependent contrasting phenomena at K and K′ valleys in monolayer semiconductors have led to addressable valley degree of freedom, which is the cornerstone for emerging valleytronic applications in information storage and processing. Tunable and active modulation of valley dynamics in a monolayer WSe 2 is demonstrated at room temperature through controllable chiral Purcell effects in plasmonic chiral metamaterials. The strong spindependent...

show abstract

Optical control of room-temperature valley polaritons

Cited by 188 publications

References 35 publications

Engineering Valley Polarization of Monolayer WS₂: A Physical Doping Approach

Engineering Valley Polarization of Monolayer WS₂: A Physical Doping Approach

Recent Progress on Exciton Polaritons in Layered Transition‐Metal Dichalcogenides

Room‐Temperature Active Modulation of Valley Dynamics in a Monolayer Semiconductor through Chiral Purcell Effects

Contact Info

Product

Resources

About

Optical control of room-temperature valley polaritons

Cited by 188 publications

References 35 publications

Engineering Valley Polarization of Monolayer WS2: A Physical Doping Approach

Engineering Valley Polarization of Monolayer WS2: A Physical Doping Approach

Recent Progress on Exciton Polaritons in Layered Transition‐Metal Dichalcogenides

Room‐Temperature Active Modulation of Valley Dynamics in a Monolayer Semiconductor through Chiral Purcell Effects

Contact Info

Product

Resources

About

Engineering Valley Polarization of Monolayer WS₂: A Physical Doping Approach

Engineering Valley Polarization of Monolayer WS₂: A Physical Doping Approach