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Time-Resolved Visualization of Laser-Induced Heating of Gold with MeV Ultrafast Electron Diffraction

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Chinese physics Letters 2014年第11期31卷 111-114页

作者：朱鹏飞傅费超刘圣广向导张杰曹建明 Key laboratory for Laser Plasmas (Ministry of Education) Department of Physics and Astronomy Shanghai Jiao Tong University Shanghai 200240 department of physics and national high magnetic field laboratory Florida State University Tallahassee Florida 32310 USA

Time-resolved electron diffraction employing MeV electron beams is demonstrated experimentally at the center for ultrafast diffraction and microscopy of Shanghai Jiao Tong University. A high-quality diffraction pattern is recorded by a single shot of electron pulse. Synchronization between the pump laser and the probe electron beam is achieved through measurement of electron deflection caused by the laser-induced plasmas in a metal tip. We study the ultrafast structural dynamics of the gold lattice excited by a femtosecond laser through tracing the change of Bragg peaks intensity at different time delays. It is expected that the combination of MeV ultrashort electron beams and femtoseeond laser pulses will open many new opportunities in the ultrafast and ultrasmall world.

关键词： HEATING of metals GOLD ELECTRON diffraction ELECTRON beams physics research

Simulation of time bunching for a pulsed positron beam

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Chinese physics B 2008年第11期17卷 4149-4152页

作者：高传波熊涛郗传英翁惠民叶邦角韩荣典周先意 department of Modern physics University of Science and Technology of China high magnetic field laboratory Hefei Institutes of Physical Science Chinese Academy of Sciences

Simulate anneal arithmetic has been used to settle the problem of time bunching on a pulsed slow-positron beam device. This paper has searched for the parameters of the device in a large scope and achieved the time re... 详细信息

关键词： pulsed positron beam time resolution simulate anneal arithmetic

Superconductivity with peculiar upper critical fields in quasi-one-dimensional Cr-based pnictides

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Chinese physics B 2018年第10期27卷 15-26页

作者： Guang-Han Cao Zeng-Wei Zhu department of physics Zhejiang University Hangzhou 310027 China Wuhan national high magnetic field Center School of Physics Huazhong University of Science and Technology Wuhan 430074 China

The discovery of superconductivity in quasi-one-dimensional Cr-based pnictides A2Cr3As3（A = alkali metals） has generated considerable research interest, primarily owing to their reduced dimensionality, significant electron correlations,and possible unconventional superconductivity. The upper critical field（Hc2） provides important information on the superconducting pairing. In this paper, we first briefly overview the latest research progress on the Cr-based ***, we introduce typical Hc2（T） behaviors of type-II superconductors in relation with the pair-breaking *** a description of the measurement method for Hc2, we focus on the analysis of Hc2 data, especially for the temperature and angle dependence, in K2Cr3As3 crystals. The result indicates（i） an absence of Pauli-paramagnetic pair breaking for field perpendicular to the Cr3As3 chains, and（ii） a unique threefold modulation for the in-plane Hc2Φ profile. Finally we conclude with remarks on the possible unconventional superconducting pairing symmetry.

关键词： Cr-based superconductors upper critical fields unconventional superconductivity

Effect of ceria surface facet on stability and reactivity of isolated platinum atoms

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Nano Research 2022年第7期15卷 5922-5932页

作者： Bochuan Song Shuxin Si Asiye Soleymani Yan Xin Helena E.Hagelin-Weaver department of Chemical Engineering University of FloridaGainesville 32611USA national high magnetic field laboratory Florida State UniversityTallahassee 32310USA

Well-defined surface structures and uniformity are key factors in exploring structure–activity relationships in heterogeneous catalysts.A modified atomic layer deposition method and three well-defined CeO_(2) nanoshapes,octahedra with(111)surfaces,cubes exposing(100)facets,and rods with(100)and(110)surface facet terminations,were utilized to synthesize ultra-low loading Pt/CeO_(2) catalysts and allow investigations on the influence of ceria surface facet on isolated Pt species under reducing conditions.A mild reduction temperature(150℃)reduces the initial platinum ions present on the surfaces of the ceria support but preserves the isolated Pt atoms on all ceria surface *** contrast,a reduction temperature of 350°C,reveals very different interactions between the initial single Pt atoms and the various ceria surface facets,leading to dissimilar and nonuniform Pt ensembles on the three ceria *** isolate facet dependent Pt–CeO_(2) interactions and avoid variations between Pt species,the Pt1/CeO_(2) catalysts after reduction at 150°C were subjected to CO oxidation *** isolated Pt atoms on the CeO_(2) octahedra and cubes are less active in the CO oxidation reaction,compared with Pt on CeO_(2) *** the case of Pt on the CeO_(2) octahedra this is due to strongly bound CO blocking active sites together with a stable CeO_(2)(111)surface limiting the oxygen supply from the *** the CeO_(2) cubes,some Pt is not available for reaction and CO is bound strongly on the available Pt *** addition,the Pt catalysts supported on the CeO_(2) cubes are not stable with time on *** isolated Pt atoms on the CeO_(2) rods are considerably more active under these conditions and this is due to a weaker Pt–CO bond strength and more facile reverse oxygen spillover from the defect-rich(110)surfaces of the rods due to the lower energy of oxygen vacancy formation on this CeO_(2) *** Pt supported on the CeO_(2) rods is also remarkably stable with t

关键词： single atom catalyst CeO_(2)shapes facet effects Pt1/CeO_(2) diffuse reflectance infrared Fourier transform spectroscopy(DRIFTS)

Experimental simulation of the Unruh effect on an NMR quantum simulator

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Science China(physics,Mechanics & Astronomy) 2016年第3期59卷 48-55页

作者： Fang Zhou Jin Hong Wei Chen Xing Rong Hui Zhou Ming Jun Shi Qi Zhang Chen Yong Ju Yi Fu Cai Shun Long Luo Xin Hua Peng Jiang Feng Du Hefei national laboratory for Physical Sciences at the Microscale and department of Modern physics University of Science and Technology of China high magnetic field laboratory Chinese Academy of Sciences Academy of Mathematics and Systems Science Chinese Academy of Sciences

The Unruh effect is one of the most fundamental manifestations of the fact that the particle content of a field theory is observer dependent. However, there has been so far no experimental verification of this effect, as the associated temperatures lie far below any observable threshold. Recently, physical phenomena, which are of great experimental challenge, have been investigated by quantum simulations in various fields. Here we perform a proof-of-principle simulation of the evolution of ferrnionic modes under the Unruh effect with a nuclear magnetic resonance （NMR） quantum simulator. By the quantum simulator, we experimentally demonstrate the behavior of Unruh temperature with acceleration, and we fiarther investigate the quantum correlations quantified by quantum discord between two fermionic modes as seen by two relatively accelerated observers. It is shown that the quantum correlations can be created by the Unrtfia effect from the classically correlated states. Our work may provide a promising way to explore the quantum physics of accelerated systems.

关键词： quantum simulation Unruh effect quantum correlations

Improving the Solidified Structure by Optimization of Coil Configuration in Pulsed Magneto-Oscillation

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Acta Metallurgica Sinica(English Letters) 2018年第12期31卷 1334-1344页

作者： Jing Zhao Ji-Hao Yu Ke Han Hong-Gang Zhong Ren-Xing Li Qi-Jie Zhai department of Mechanical and Electrical Engineering Tangshan University State Key laboratory of Advanced Special Steel Shanghai University national high magnetic field laboratory Florida State University

Using both numerical and experimental methods, we studied the effect of coil configuration of pulsed magneto-oscillation（PMO） on distribution of electromagnetic field, flow field and solidification structure with the same pulse currentparameters in A1 ingots. We designed and constructed three types of coils： surface pulsed magneto-oscillation, hot-toppulsed magneto-oscillation （HPMO） and combined pulsed magneto-oscillation （CPMO）. PMO treatment refined thesolidification structure in all the ingots. The configuration of the PMO, however, introduced differences in magnetic fieldintensity, electromagnetic force, Joule heat, flow field, equiaxed grain zone, grain size and growth direction of columnargrains. The largest equiaxed grain zone was found in CPMO treated ingot, and the smallest grain size was found in bothHPM0 and CPMO treated ingots. Numerical simulation indicated that difference in electromagnetic field and flow fieldresulted in differences in solidification structure. HPMO is more advantageous over others for large ingot production.

关键词： Pulsed magneto-oscillation Coil configuration Electromagnetic field Flow field Solidification structure Optimization

Applicability of the vortex-glass model for the single crystal Tl_(0.4)K_(0.41)Fe_(1.71)Se_2

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Chinese physics B 2015年第1期24卷 462-466页

作者：于一汪春昌汪洪李秋菊张昌锦皮雳张裕恒 School of physics and Material Science Anhui University high magnetic field laboratory Chinese Academy of Sciences and University of Science and Technology of China Hefei national laboratory for Physical Sciences at the Microscale

We measure the current–voltage（I–V） characteristics for the single crystal of Tl0.4K0.41Fe1.71Se2 with the superconducting transition temperature（TC） around 30.5 K, under a 10 T magnetic field applied perpendicular and parallel to the ab plane. We find that the shapes of the I–V isotherms are very different from the description by the vortex-glass（VG） *** theoretical calculations and analysis of the ρH⊥ab–T and ρH ab–T data, we give an explicit discussion over the suitability of the VG model for the A0.8Fe2Se2 superconductors, and point out the possibility of the material acting as a convenient platform for re-examination and further study of the complex vortex behaviors in the layered superconductors.

关键词： iron-based superconductor vortex-glass model flux flow pinning

Multiband nodeless superconductivity near the charge-density-wave quantum critical point in ZrTe(3-x)Sex

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Chinese physics B 2016年第7期25卷 89-92页

作者：崔珊何兰坡洪晓晨朱相德 Cedomir Petrovic 李世燕 State Key laboratory of Surface physics Department of Physics and Laboratory of Advanced MaterialsFudan University high magnetic field laboratory Chinese Academy of Sciences and University of Science and Technology of China Condensed Matter physics and Materials Science department Brookhaven National Laboratory Collaborative Innovation Center of Advanced Microstructures

It was found that selenium doping can suppress the charge-density-wave（CDW） order and induce bulk superconductivity in ZrTe3. The observed superconducting dome suggests the existence of a CDW quantum critical point（QCP） in ZrTe3-xSex near x ≈ 0.04. To elucidate the superconducting state near the CDW QCP, we measure the thermal conductivity of two ZrTe（3-x）Sex single crystals（x = 0.044 and 0.051） down to 80 m K. For both samples, the residual linear term κ0/T at zero field is negligible, which is a clear evidence for nodeless superconducting gap. Furthermore, the field dependence of κ0/T manifests a multigap behavior. These results demonstrate multiple nodeless superconducting gaps in ZrTe（3-x）Sex,which indicates conventional superconductivity despite of the existence of a CDW QCP.

关键词： superconductivity charge-density-wave order thermal transport measurement gap structure

Near-perfect replication on amorphous alloys through active force modulation based on machine learning/neural network parameter prediction

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Science China(physics,Mechanics & Astronomy) 2025年第1期Mechanics & Astronomy) .卷 181-191页

作者： Senkuan Meng Zheng Wang Ruisong Zhu Ruijie Liu Jiang Ma Lina Hu Weihua Wang Key laboratory for Liquid-Solid Structural Evolution and Processing of Materials (Ministry of Education) School of Materials Science and Engineering Shandong University College of Mechatronics and Control Engineering Shenzhen University Songshan Lake Materials laboratory Institute of physics Chinese Academy of Sciences

As a microforming technique, micro/nano-structural replication possesses advantages of high precision and efficiency. With the remarkable superplasticity in the supercooled liquid region, amorphous alloys or metallic glasses(MGs) are regarded as ideal materials for miniature fabrication. However, due to the intrinsic metastable nature of supercooled liquids, the design of imprinting processes for MGs poses a challenge. In the past, process parameters have largely relied on trial-and-error *** this work, a low-frequency active force modulation system is employed to apply a stable, precise, and real-time feedback stress field for imprinting of MG samples. Low-frequency vibrations can facilitate the filling of microstructures on the template surface by reducing the effective viscosity of the supercooled liquid. With the dataset composed of orthogonal experiments, a machine learning strategy based on back-propagation(BP) neural networks was utilized to construct a 3D parameter space for temperature, stress, and time, and to predict the corresponding filling ratio. Furthermore, the optimal combination of imprinting process parameters was identified, and its filling ratio was experimentally validated to reach as high as 0.94. The near-perfect replication of microstructures confirms the superiority of the active force modulation system and the data-driven strategy of machine learning-assisted parameter design. At the same time, this one-step microforming process provides a new approach to addressing the accuracy-cost trade-off dilemma in precision manufacturing.

关键词： metallic glass amorphous alloy microforming imprinting machine learning