- 标题
- 摘要
- 关键词
- 实验方案
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Dynamics of phase separation from holography
摘要： We use holography to develop a physical picture of the real-time evolution of the spinodal instability of a four-dimensional, strongly-coupled gauge theory with a first-order, thermal phase transition. We numerically solve Einstein’s equations to follow the evolution, in which we identify four generic stages: a first, linear stage in which the instability grows exponentially; a second, non-linear stage in which peaks and/or phase domains are formed; a third stage in which these structures merge; and a fourth stage in which the system finally relaxes to a static, phase-separated configuration. On the gravity side the latter is described by a static, stable, inhomogeneous horizon. We conjecture and provide evidence that all static, non-phase separated configurations in large enough boxes are dynamically unstable. We show that all four stages are well described by the constitutive relations of second-order hydrodynamics that include all second-order gradients that are purely spatial in the local rest frame. In contrast, a Müller-Israel-Stewart-type formulation of hydrodynamics fails to provide a good description for two reasons. First, it misses some large, purely-spatial gradient corrections. Second, several second-order transport coefficients in this formulation, including the relaxation times τπ and τΠ, diverge at the points where the speed of sound vanishes.
关键词： Gauge-gravity correspondence,Holography and quark-gluon plasmas,AdS-CFT Correspondence
更新于2025-09-19 17:13:59
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Decoding the structure of interfaces and impurities in 2D materials by photoelectron holography
摘要： The properties of atomically thin materials essentially depend on their structures, including impurities, defects and interfaces with underlying substrates. Thus, the detailed structural information is relevant for creation of 2D materials with desired properties. Here, we explore the capabilities of photoelectron diffraction and holography for structural analysis of atomically thin layers using as examples such systems as h-BN, graphene, and modified graphene with boron impurities. We show that for planar 2D crystals with commensurate interface to the substrate, it is possible to visualize the interface and impurities with high spatial resolution, and to distinguish possible non-equivalent structural units. Our approach applied to B-doped graphene on Ni(1 1 1) and Co(0 0 0 1) surfaces has allowed to reveal asymmetry of boron concentrations in the two carbon sublattices and established its dependence on the applied synthesis procedure and chosen substrate. The obtained results suggest that such approach can be widely applied for studies of various 2D systems, where the structures of interfaces and defects are of remarkable importance.
关键词： doping,structure,photoelectron diffraction,graphene,hexagonal boron nitride,photoelectron holography
更新于2025-09-19 17:13:59
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Local structural analysis of Pb(Fe <sub/>1/2</sub> Nb <sub/>1/2</sub> )O <sub/>3</sub> multiferroic material using X-ray fluorescence holography
摘要： We performed X-ray fluorescence holography measurements on a Pb(Fe1/2Nb1/2)O3 (PFN) multiferroic material in order to investigate the temperature dependence of three dimensional local structure around Fe atoms. It was found that the atomic image intensity of the nearest neighbor Pb atom abruptly decreases when the temperature becomes lower than the Néel temperature (TN) of about 150 K, while the intensity of the atomic image at nearest Fe/Nb position remains almost unchanged. These observations show that the magnetic transition at TN induces static positional shifts of Pb atoms but does not strongly influence the Fe/Nb atoms, which suggests the involvement of Pb ions into the superexchange interaction between Fe ions and its contribution to the spin-lattice coupling in PFN.
关键词： Pb(Fe1/2Nb1/2)O3,local structure,X-ray fluorescence holography,multiferroic material,temperature dependence
更新于2025-09-19 17:13:59
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Precise Potential Observation of a Biased GaAs p-n Junction by <i>in situ</i> Phase-shifting Electron Holography; é????§??°??????GaAs p-n??￥??????é???2??o|é???-??·??????-??°????????￡???????????′è|3?ˉ?;
摘要： 昨今，半導体デバイスの研究開発において，動作中の電位温度 120 K の低温下でバルク試料の一部を薄膜化することにより作製した．この試料を電圧印加用 TEM 試料ホルダーにセットし，外部電源と電気的に接続することで TEM 内試料への電圧印加を可能とした．観察はホログラフィー電子顕微鏡(HF3300EH)を用いて加速電圧 300 kV で実施した．位相シフト法による位相再生には，入射電子線の初期位相をシフトして撮影した50枚のホログラムを用いた．
关键词： pn junction,cooling focused ion beam,electron beam holography
更新于2025-09-19 17:13:59
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Data processing for atomic resolution holography
摘要： In photoelectron holography, the intensity of the angular distribution of photoelectrons is measured to obtain a hologram. Thus, a hologram can be defined as a function on a sphere. X-ray fluorescence holography is similar to photoelectron holography. In this study, we describe methods for representing spherical functions that are suitable for atomic resolution holography, and the theory of conversion from the coordinate system of measurement to the various projections. We describe methods for rotational transformations and symmetry operations for atomic resolution hologram and the image composition from measured hologram fragments. In addition, several ways to remove the background from the raw hologram data are discussed.
关键词： atomic resolution holography,photoelectron holography,X-ray fluorescence holography,background removal,spherical functions,symmetry operations,rotational transformations,image composition
更新于2025-09-16 10:30:52
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X-ray fluorescence holography for soft matter
摘要： X-ray fluorescence holography (XFH) is a technique that can directly image the 3D arrangement of atoms around an element in a sample. The holograms contain both intensity and phase information, allowing atomic reconstruction without needing prior structural information or a tentative structural model. XFH has already been used to reveal the local structures of various inorganic samples, and recently, work has begun on XFH for soft matter. In this paper, we review the progress of XFH on soft materials. First, we review the fundamental principles of XFH. Second, we review inverse mode XFH on soft materials, and the results of the experiments on hemoglobin, myoglobin, and κ-(BEDT-TTF)2Cu[N(CN)2]Br crystals. In the last section, we report the progress of the development of normal mode holography for soft materials. The new apparatus and scanning method is described, and results of the initial tests on the protein Photosystem II are discussed.
关键词： normal mode holography,atomic reconstruction,X-ray fluorescence holography,inverse mode XFH,soft matter
更新于2025-09-16 10:30:52
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Reflection in-line and off-axis hybrid digital holography
摘要： We propose an in-line and off-axis hybrid holographic method for imaging reflective objects. The in-line and off-axis digital holograms are recorded by a Michelson interferometer. The approximate phase of object wave is obtained by spectral filtering approach from the off-axis hologram, and it is used as an initial input in an iterative procedure for retrieving the complex field of the object from the in-line hologram. In this way, the output of the iterative procedure can produce higher quality amplitude and phase images compared to only in-line or off-axis digital holography. The performance of this method has been demonstrated by acquiring the amplitude and phase images of a resolution target and a microelectronic chip.
关键词： Reflective object,Phase retrieval,Spectral filtering,Digital holography
更新于2025-09-16 10:30:52
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[IEEE 2019 International Conference on Optical MEMS and Nanophotonics (OMN) - Daejeon, Korea (South) (2019.7.28-2019.8.1)] 2019 International Conference on Optical MEMS and Nanophotonics (OMN) - Metasurfaces for Display and Imaging Applications
摘要： Metasurfaces composed of subwavelength nanostructures have shown unprecedented abilities to control electromagnetic waves, and have been expected to be applied for the next generation imaging devices. In this keynote talk, general introduction of optical metasurfaces will be introduced with their physical instruments and applications. Then, we will discuss recent advances on metasurface applications for holography and augmented reality. In particular, full complex-amplitude modulated holograms and ultra-wide augmented reality imaging will be mainly discussed with our theoretical and experimental demonstrations. Our perspectives for the future of this area will also be discussed.
关键词： Metasurface,Augmented Reality,Optical display,Holography
更新于2025-09-16 10:30:52
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[IEEE 2018 17th Workshop on Information Optics (WIO) - Québec, QC, Canada (2018.7.16-2018.7.19)] 2018 17th Workshop on Information Optics (WIO) - Grating-assisted spatial phase-shifting incoherent digital holography with compressive sensing for noise reduction
摘要： We have proposed grating-assisted spatial phase-shifting incoherent digital holography for capturing holograms of dynamically moving objects. With our method, four individual self-reference holograms of a spatially incoherent light are simultaneously created on an image sensor. Thus, it is possible to detect complex amplitude distribution from a single captured image by using a phase-shifting technique. In the present study, we aim to improve the quality of reconstructed images in our method by introducing compressive sensing. To validate the effectiveness of compressive sensing in our method, a 3D image was reconstructed from detected complex amplitude distribution by enforcing the sparsity constraint on the total variation of a signal. As a result, the introduction of compressive sensing can effectively reduce noise and out-of-focus artifacts in our method.
关键词： phase-shifting interferometer,3D imaging,diffractive optical element,compressive sensing,digital holography
更新于2025-09-16 10:30:52
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Flat-space holography and correlators of Robinson–Trautman stress tensor
摘要： We propose a quasi-local stress tensor for the four-dimensional asymptotically flat Robinson–Trautman geometries by taking the flat-space limit from the corresponding asymptotically AdS solutions. This stress tensor results in the correct charges of the generators of BMS symmetry if we define conformal infinity by an anisotropic scaling of the metric components. Using flat-space holography this stress tensor is related to expectation values of the stress tensor in a dual field theory called BMS-invariant field theory (BMSFT). We also calculate the two and three point functions of the proposed stress tensor.
关键词： Flat-space holography,BMSFT,Robinson–Trautman geometry
更新于2025-09-16 10:30:52