The pressure-induced color change in the nitrogen-doped lutetium hydride has triggered extensive discussions about the underlying physics and potential applications.Here,we study the optical response of LuH_(2±x)...The pressure-induced color change in the nitrogen-doped lutetium hydride has triggered extensive discussions about the underlying physics and potential applications.Here,we study the optical response of LuH_(2±x)N_(y)in a broad frequency range at ambient pressure and its evolution with pressure in the visible spectral range.The broad-band optical spectra at ambient pressure reveal a Drude component associated with intra-band electronic transitions and two Lorentz components(L1 and L2)arising from inter-band electronic transitions.The application of pressure causes a spectral weight transfer from L1 to the Drude component,leading to a blue shift of the plasma edge in the reflectivity spectrum alongside a reduction of the high-frequency reflectivity.Our results suggest that the pressure-induced color change in LuH_(2±x)N_(y)is closely related to the transformation between intra-and inter-band electronic transitions,providing new insights into the mechanism of the pressure-induced color change in LuH_(2±x)N_(y).展开更多
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
Animals always seek rewards and the related neural basis has been well studied. However, what happens when animals fail to get a reward is largely unknown,although this is commonly seen in behaviors such as predation....Animals always seek rewards and the related neural basis has been well studied. However, what happens when animals fail to get a reward is largely unknown,although this is commonly seen in behaviors such as predation. Here, we set up a behavioral model of repeated failure in reward pursuit(RFRP) in Drosophila larvae. In this model, the larvae were repeatedly prevented from reaching attractants such as yeast and butyl acetate, before finally abandoning further attempts. After giving up, they usually showed a decreased locomotor speed and impaired performance in light avoidance and sugar preference,which were named as phenotypes of RFRP states. In larvae that had developed RFRP phenotypes, the octopamine concentration was greatly elevated, while tbh mutants devoid of octopamine were less likely to develop RFRP phenotypes, and octopamine feeding efficiently restored such defects. By down-regulating tbh in different groups of neurons and imaging neuronal activity, neurons that regulated the development of RFRP states and the behavioral exhibition of RFRP phenotypes were mapped to a small subgroup of non-glutamatergic and glutamatergic octopaminergic neurons in the central larval brain. Our results establish a model for investigating the effect of depriving an expected reward in Drosophila and provide a simplified framework for the associated neural basis.展开更多
基金supported by the National Key R&D Program of China(Grant Nos.2022YFA1403201,and 2022YFA1404700)the National Natural Science Foundation of China(Grant Nos.12174180,12074085,12204231,and 12061131001)+1 种基金the Fundamental Research Funds for the Central Universities(Grant No.020414380095)the Jiangsu Shuangchuang Program。
文摘The pressure-induced color change in the nitrogen-doped lutetium hydride has triggered extensive discussions about the underlying physics and potential applications.Here,we study the optical response of LuH_(2±x)N_(y)in a broad frequency range at ambient pressure and its evolution with pressure in the visible spectral range.The broad-band optical spectra at ambient pressure reveal a Drude component associated with intra-band electronic transitions and two Lorentz components(L1 and L2)arising from inter-band electronic transitions.The application of pressure causes a spectral weight transfer from L1 to the Drude component,leading to a blue shift of the plasma edge in the reflectivity spectrum alongside a reduction of the high-frequency reflectivity.Our results suggest that the pressure-induced color change in LuH_(2±x)N_(y)is closely related to the transformation between intra-and inter-band electronic transitions,providing new insights into the mechanism of the pressure-induced color change in LuH_(2±x)N_(y).
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.
基金supported by National Basic Research Development Program of China (973 Program, 2013CB945603)the National Natural Science Foundation of China (31070944, 31271147, 31471063, 31671074)+1 种基金the Natural Science Foundation of Zhejiang Province (LR13C090001)the Fundamental Research Funds for the Central Universities, China (No. 2017FZA7003)
文摘Animals always seek rewards and the related neural basis has been well studied. However, what happens when animals fail to get a reward is largely unknown,although this is commonly seen in behaviors such as predation. Here, we set up a behavioral model of repeated failure in reward pursuit(RFRP) in Drosophila larvae. In this model, the larvae were repeatedly prevented from reaching attractants such as yeast and butyl acetate, before finally abandoning further attempts. After giving up, they usually showed a decreased locomotor speed and impaired performance in light avoidance and sugar preference,which were named as phenotypes of RFRP states. In larvae that had developed RFRP phenotypes, the octopamine concentration was greatly elevated, while tbh mutants devoid of octopamine were less likely to develop RFRP phenotypes, and octopamine feeding efficiently restored such defects. By down-regulating tbh in different groups of neurons and imaging neuronal activity, neurons that regulated the development of RFRP states and the behavioral exhibition of RFRP phenotypes were mapped to a small subgroup of non-glutamatergic and glutamatergic octopaminergic neurons in the central larval brain. Our results establish a model for investigating the effect of depriving an expected reward in Drosophila and provide a simplified framework for the associated neural basis.