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《中国物理 B》2021,30(6):66701-066701
Floquet theorem is widely used in the light-driven systems. But many 2 D-materials models under the radiation are investigated with the high-frequency approximation, which may not be suitable for the practical experiment. In this work,we employ the non-perturbative Floquet method to strictly investigate the photo-induced topological phase transitions and edge states properties of graphene nanoribbons under the light irradiation of different frequencies(including both low and high frequencies). By analyzing the Floquet energy bands of ribbon and bulk graphene, we find the cause of the phase transitions and its relation with edge states. Besides, we also find the size effect of the graphene nanoribbon on the band gap and edge states in the presence of the light. 相似文献
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Erratum to “Floquet bands and photon-induced topological edge states of graphene nanoribbons” 
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下载免费PDF全文 Weijie Wang 《中国物理 B》2021,30(11):119901-119901
Figures 2(a) and 2(b) in the original paper [Chin. Phys. B 30 066701 (2021)] are replaced by the new ones. 相似文献
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Applying a many mode Floquet formalism for magnetically trapped atoms interacting with a polychromatic rf-field, we predict a large two photon transition probability in the atomic system of cold 87Rb atoms. The physical origin of this enormous increase in the two photon transition probability is due to the formation of avoided crossings between eigen-energy levels originating from different Floquet sub-manifolds and redistribution of population in the resonant intermediate levels to give rise to the resonance enhancement effect. Other exquisite features of the studied atom-field composite system include the splitting of the generated avoided crossings at the strong field strength limit and a periodic variation of the single and two photon transition probabilities with the mode separation frequency of the polychromatic rf-field. This work can find applications to characterize properties of cold atom clouds in the magnetic traps using rf-spectroscopy techniques. 相似文献
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2D materials are promising but remain to be further explored, with respect to their usage in various optoelectronic devices. Generally, 2D materials exhibit far less than ideal absorption due to their thickness, limiting their deployment in practical optoelectronic applications. To address this challenge, extensive research has been performed utilizing different designs, such as distributed Bragg reflector microcavities, metallic reflectors, photonic crystal nanocavities, and plasmonic nanostructures, to confine light within 2D materials and increase light absorption. Recent progresses in enhancing light absorption in graphene and other 2D materials such as transition metal dichalcogenides and phosphorene are reviewed. Some physical mechanisms that realize enhanced absorption in 2D materials, as well as their potential applications are also discussed. 相似文献
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近年来, 自组装纳米结构因为其容易制备、稳定、环保以及与各种功能基团、粒子等的多样结合能力吸引了科学家们的目光, 成为人们研究的热点课题, 在光电池、光催化、水凝胶、药物缓释等方面的实验科学领域得到了广泛的应用. 尤其是光催化方面, 自组装结构的重复性为激子的传递创造了比较良好的条件, 成为众多激子传递平台中的佼佼者. 本文报道了一种以苯丙氨酸二肽纳米管和羧基石墨烯为基础的自组装光吸收催化平台, 对其结构进行研究, 并使用该体系进行了烟酰胺腺嘌呤二核苷酸到它的还原态的催化实验. 该体系的微观结构由纳米管和石墨烯膜复合而成, 羧基石墨烯的存在能够降低纳米管直径, 实现纳米管的形态操控, 石墨烯与多肽纳米管复合纳米结构的存在实现了多通道协同激子传递, 降低了激子传递的距离, 极大增强了催化中心对于激子的接受和使用效率. 在复合了光敏剂和催化中心之后, 该体系具有较高的稳定性, 均一的分散性, 很强的光能吸收和转化能力等性质. 对于从NADP+往NADPH转变的催化实验表明, 该体系有较高的反应速率和催化效率, 并且比两种单一结构催化平台效果之和更好, 实现了一加一大于二的效应, 展现了复合纳米结构光吸收催化平台的巨大潜力和广阔应用前景. 相似文献
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Jing Chen Jiangyong Pan Qianqian Huang Feng Xu Zichen Zhang Wei Lei Arokia Nathan 《physica status solidi (a)》2015,212(12):2856-2861
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Xingfei Zhou 《中国物理 B》2022,31(4):47301-047301
We investigate the electron retroreflection and the Klein tunneling across a graphene-based n-p-n junction irradiated by linearly polarized off-resonant light with the polarization along the x direction. The linearly polarized off-resonant light modifies the band structure of graphene, which leads to the anisotropy of band structure. By adjusting the linearly polarized light and the direction of n-p-n junction simultaneously, the electron retroreflection appears and the anomalous Klein tunneling, the perfect transmission at a nonzero incident angle regardless of the width and height of potential barrier, happens, which arises from the fact that the light-induced anisotropic band structure changes the relation of wavevector and velocity of electron. Our finding provides an alternative and flexible method to modulate electron retroreflection and Klein tunneling. 相似文献
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Yuhan Zhong Xiao Lin Jing Jiang Yi Yang Gui-Geng Liu Haoran Xue Tony Low Hongsheng Chen Baile Zhang 《Laser u0026amp; Photonics Reviews》2021,15(4):2000388
Directional excitation of guidance modes is central to many applications ranging from light harvesting, optical information processing to quantum optical technology. Of paramount interest, especially, the active control of near-field directionality provides a new paradigm for the real-time on-chip manipulation of light. Here, it is found that for a given dipolar source, its near-field directionality can be toggled efficiently via tailoring the polarization of surface waves that are excited, for example, via tuning the chemical potential of graphene in a graphene-metasurface waveguide. This finding enables a feasible scheme for the active near-field directionality. Counterintuitively, it is revealed that this scheme can transform a circular electric/magnetic dipole into a Huygens dipole in the near-field coupling. Moreover, for Janus dipoles, this scheme enables actively flipping their near-field coupling and non-coupling faces. 相似文献
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Biao Huang 《Frontiers of Physics》2023,18(1):13601
We review the recent development in constructing higher-order topological band insulators under strong periodic drivings. In particular, we focus on various approaches in formulating the anomalous Floquet topological invariants beyond (quasi-)static band topology, and compare their different physical consequences. 相似文献
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We present explicit expressions for the Floquet states of a periodically kicked particle in coordinate and momentum representations.
These states have been used to evaluate the energy of the particle after an arbitrary number of kicks. 相似文献
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《Current Applied Physics》2018,18(2):163-169
Nitrogen-doped TiO2 coatings on reduced graphene oxide were prepared via a sonochemical synthesis and hydrothermal process. The nanocomposites showed improved photocatalytic activity due to their large specific surface areas (185–447 m2/g), the presence of TiO2 in the anatase phase, and a quenched photoluminescence peak. In particular, GN3-TiO2 (nitrogen-doped TiO2 coatings on rGO with 3 ml of titanium (IV) isopropoxide) exhibited the best photocatalytic efficiency and degradation rate among the materials prepared. With nitrogen-doped on the reduced graphene oxide surface, the photocatalytic activity is enhanced approximately 17.8 times compared to that of the pristine TiO2. The dramatic enhancement of activity is attributed to the nitrogen contents and rGO effectively promoting charge-separation efficiency and providing abundant catalytically active sites to enhance the reactivity. The composites also showed improved pollutant adsorption capacity, electron–hole pair lifetime, light absorption capability, and absorbance of visible light. 相似文献
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《Advanced Optical Materials》2017,5(3)
Modulation of visible light has been easily achieved for decades, but modulation of terahertz (THz) light still remains a challenge. To address this issue, the Fresnel equations have been developed to describe a conductive interface in a total internal reflection geometry and reveal a new approach for modulation. To demonstrate this new mechanism, a broadband device achieving a modulation depth greater than 90% between 0.15 and 0.4 THz, and reaching a maximum of 99.3% at 0.24 THz has been designed. The modulation is achieved by applying a gate voltage between −0.1 and 2 V to a graphene layer in a total internal reflection geometry. Compared to conventional designs, the high modulation is realized without assistance from metamaterial structures, resonant cavities, or multistacked graphene layers. Thus, the design is efficient and easy‐to‐fabricate and can be easily retrofitted to most existing THz systems. This work opens up a new avenue of research as the device has verified the theory and demonstrates how it can be used to make practical devices, bringing a promising new paradigm for THz modulation, thin‐film sensing, and noninvasive material characterization. 相似文献
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Matthias J. Grotevent Claudio U. Hail Sergii Yakunin Dmitry N. Dirin Kishan Thodkar Gabriela Borin Barin Philippe Guyot‐Sionnest Michel Calame Dimos Poulikakos Maksym V. Kovalenko Ivan Shorubalko 《Advanced Optical Materials》2019,7(11)
Photodetectors utilizing graphene field‐effect transistors sensitized by colloidal quantum dots exhibit high responsivities under infrared light illumination. Precise, microscopic spatial control over quantum dot deposition is required to gain deeper insight into device mechanisms, optimize device performance, and enable new device architectures and applications. The latter may eventually include photodetectors with subwavelength device dimensions. Here, infrared photodetectors are fabricated by electrohydrodynamic nanoprinting of colloidal PbS quantum dots onto graphene field‐effect transistors with varying quantum dot layer thicknesses on a single substrate, demonstrating the potential of the method for realizing small footprint detectors with high spatial resolution. Remarkably, while the responsivity of the photodetectors increases with increasing layer thicknesses up to 130 nm, the noise current is found to be independent of the layer thickness. In addition, the responsivity and noise current are both linearly dependent on the applied drain voltage and drain current. As a result, the specific detectivity is independent of the drain voltage, and the detector can be operated at lower drain voltages thus reducing power consumption. Finally, specific detectivities of at least 109 Jones at 1200 nm are obtained, without degradation of the charge carrier mobilities in graphene from the electrohydrodynamic printing. 相似文献
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《Advanced Optical Materials》2018,6(13)
Graphene grown by chemical vapor deposition has attracted much attention in optoelectronic application due to its great potential as a large‐area 2D electrode material. However, the clean transfer and effective microscale patterning of graphene still remain great challenges for its use as the electrode in the optoelectronic devices. In this paper, a simple and reliable transfer‐pattern strategy is developed for the microscale‐patterned graphene electrode by using a photoresist as both supporting layer for the graphene transfer and photolithographic mask layer. The microscale‐patterned graphene electrodes transferred onto the desired substrates exhibit low surface roughness of 0.675 nm and mean sheet resistance of 444 Ω ◽−1. 25 µm line width patterned organic light‐emitting devices (OLEDs) arrays with high precision and uniform lighting area have proved the great potential of the transfer‐pattern strategy for high‐resolution OLEDs. Flexible and efficient OLEDs based on patterned graphene anodes can be realized by this strategy. Moreover, a scale of ≈2 in. patterned graphene well demonstrates the feasibility of the transfer‐pattern strategy for large‐area fabrication of the microscale‐patterned graphene. 相似文献
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The purpose of this article is to present an historical overview of theoretical approaches used for describing spin dynamics under static or rotating experiments in solid state nuclear magnetic resonance. The article gives a brief historical overview for major theories in nuclear magnetic resonance and the promising theories. We present the first application of Floquet–Magnus expansion to chemical shift anisotropy when irradiated by BABA pulse sequence. 相似文献