Naturally existing in-plane hyperbolic polaritons and the associated optical topological transitions,which avoid the nano-structuring to achieve hyperbolicity,can outperform their counterparts in artificial metasurfac...Naturally existing in-plane hyperbolic polaritons and the associated optical topological transitions,which avoid the nano-structuring to achieve hyperbolicity,can outperform their counterparts in artificial metasurfaces.Such plasmon polaritons are rare,but experimentally revealed recently in WTe_(2)van der Waals thin films.Different from phonon polaritons,hyperbolic plasmon polaritons originate from the interplay of free carrier Drude response and interband transitions,which promise good intrinsic tunability.However,tunable in-plane hyperbolic plasmon polariton and its optical topological transition of the isofrequency contours to the elliptic topology in a natural material have not been realized.Here we demonstrate the tuning of the optical topological transition through Mo doping and temperature.The optical topological transition energy is tuned over a wide range,with frequencies ranging from 429 cm^(−1)(23.3 microns)for pure WTe_(2)to 270 cm^(−1)(37.0 microns)at the 50%Mo-doping level at 10 K.Moreover,the temperature-induced blueshift of the optical topological transition energy is also revealed,enabling active and reversible tuning.Surprisingly,the localized surface plasmon resonance in skew ribbons shows unusual polarization dependence,accurately manifesting its topology,which renders a reliable means to track the topology with far-field techniques.Our results open an avenue for reconfigurable photonic devices capable of plasmon polariton steering,such as canaling,focusing,and routing,and pave the way for low-symmetry plasmonic nanophotonics based on anisotropic natural materials.展开更多
Low symmetry 2D materials with intrinsic in-plane anisotropic optical properties and high tunability provide a promising platform to explore and manipulate light–matter interactions.To date,dozens of in-plane anisotr...Low symmetry 2D materials with intrinsic in-plane anisotropic optical properties and high tunability provide a promising platform to explore and manipulate light–matter interactions.To date,dozens of in-plane anisotropic 2D materials with diverse band structures have been discovered.They exhibit rich optical properties,indicating great potential for novel applications in optics,photonics,and optoelectronics.In this paper,we thoroughly review the anisotropic optical properties and polaritons in many kinds of low symmetry 2D materials,aiming to elicit more research interest in this field.First,the optical properties of anisotropic 2D semiconductors,including interband absorption,photoluminescence,excitons,and band structure engineering for tuning optical responses,are introduced.Then fundamentals and advances in experiments of hyperbolic polaritons in anisotropic 2D materials,including phonon,plasmon,and exciton polaritons,are discussed.Finally,a perspective on promising research directions is given.展开更多
基金H.Y.is grateful to the financial support from the National Key Research and Development Program of China(Grant Nos.2022YFA1404700 and 2021YFA1400100)the National Natural Science Foundation of China(Grant No.12074085)+7 种基金the Natural Science Foundation of Shanghai(Grant No.23XD1400200)C.W.is grateful to the financial support from the National Natural Science Foundation of China(Grant Nos.12274030,11704075)the National Key Research and Development Program of China(Grant No.2022YFA1403400)F.S.acknowledges the financial support from the National Key Research and Development Program of China(Grant No.2017YFA0303203)the National Natural Science Foundation of China(Grant Nos.92161201,12025404,11904165,and 12274208)the Natural Science Foundation of Jiangsu Province(Grant No.BK20190286)S.H.is grateful to the financial support from the China Postdoctoral Science Foundation(Grant No.2020TQ0078)Part of the experimental work was carried out in Fudan Nanofabrication Lab.
文摘Naturally existing in-plane hyperbolic polaritons and the associated optical topological transitions,which avoid the nano-structuring to achieve hyperbolicity,can outperform their counterparts in artificial metasurfaces.Such plasmon polaritons are rare,but experimentally revealed recently in WTe_(2)van der Waals thin films.Different from phonon polaritons,hyperbolic plasmon polaritons originate from the interplay of free carrier Drude response and interband transitions,which promise good intrinsic tunability.However,tunable in-plane hyperbolic plasmon polariton and its optical topological transition of the isofrequency contours to the elliptic topology in a natural material have not been realized.Here we demonstrate the tuning of the optical topological transition through Mo doping and temperature.The optical topological transition energy is tuned over a wide range,with frequencies ranging from 429 cm^(−1)(23.3 microns)for pure WTe_(2)to 270 cm^(−1)(37.0 microns)at the 50%Mo-doping level at 10 K.Moreover,the temperature-induced blueshift of the optical topological transition energy is also revealed,enabling active and reversible tuning.Surprisingly,the localized surface plasmon resonance in skew ribbons shows unusual polarization dependence,accurately manifesting its topology,which renders a reliable means to track the topology with far-field techniques.Our results open an avenue for reconfigurable photonic devices capable of plasmon polariton steering,such as canaling,focusing,and routing,and pave the way for low-symmetry plasmonic nanophotonics based on anisotropic natural materials.
基金the National Key Research and Development Program of China(2022YFA1404700 and 2021YFA1400100)National Natural Science Foundation of China(12074085)+4 种基金Natural Science Foundation of Shanghai(20JC1414601)Strategic Priority Research Program of Chinese Academy of Sciences(XDB30000000)the National Key Research and Development Program of China(2022YFA1403400)the National Natural Science Foundation of China(12274030 and 11704075)the China Postdoctoral Science Foundation(2020TQ0078).
文摘Low symmetry 2D materials with intrinsic in-plane anisotropic optical properties and high tunability provide a promising platform to explore and manipulate light–matter interactions.To date,dozens of in-plane anisotropic 2D materials with diverse band structures have been discovered.They exhibit rich optical properties,indicating great potential for novel applications in optics,photonics,and optoelectronics.In this paper,we thoroughly review the anisotropic optical properties and polaritons in many kinds of low symmetry 2D materials,aiming to elicit more research interest in this field.First,the optical properties of anisotropic 2D semiconductors,including interband absorption,photoluminescence,excitons,and band structure engineering for tuning optical responses,are introduced.Then fundamentals and advances in experiments of hyperbolic polaritons in anisotropic 2D materials,including phonon,plasmon,and exciton polaritons,are discussed.Finally,a perspective on promising research directions is given.