超重核合成、准晶的新奇超导、神经网络、透射电子显微学 | 本周物理讲座

学术 2024-11-12 09:43 北京

1 Synthesis of new super heavy nuclei – our understanding and needs

报告人：Michał Kowal, National Centre for Nuclear Research

时间：11月12日（周二）10:00

单位：中国科学院理论物理研究所

地点：北楼202

摘要：

I will discuss some of the topics that we are researching and that we are currently interested in in Warsaw. All of them will be related to the physics of superheavy nuclei, where the central goal is to predict the possibility of synthesizing new elements. I'll briefly discuss

- Selected Properties of heaviest nuclei

- Competing Minima & Exotic Nuclear Configurations

- Searching for Extra Stable Systems in SHN

- Nuclear Level Densities

- Reaction Mechanism

- X-sections predictions

报告人简介：

Prof. Michał Kowal is a theoretical physicist. His scientific interests include the prediction of cross-sections (synthesis probabilities) for existing and planned super-heavy nuclei, as well as stability analysis, including the calculation of lifetimes for the heaviest nuclei. He obtained his Master’s degree and Ph.D. in Physics from Maria Curie-Sklodowska University in 1999 and 2004, respectively. He is currently an associate professor and the head of the Department of Theoretical Physics at the National Centre for Nuclear Research, Poland.

2 Electron-electron interaction driven exotic superconductivities in the quasicrystals

报告人：杨帆，北京理工大学

时间：11月12日（周二）10:00

单位：中国科学院理论物理所

地点：北楼322

摘要：

The quasicrystal represents a type of long-range-ordered structure which possesses rotational symmetry but is not periodic. The recent revelation of superconductivity (SC) in the Al-Zn-Mg and Ta-Te quasi-crystals (QCs) has aroused great interests. Here, we report our series of works on the electron-electron interaction driven exotic SCs on QCs, including both intrinsic QCs such as the Penrose tiling and extrinsic QCs such as the 45°-twisted bilayel cuprates. We generalize the Kohn-Luttinger mechanism for repulsive interaction-driven SCs from periodic lattices to QCs, and classify the pairing symmetries. Consequently, we found a series of novel superconducting phases such as the chiral SC with spontaneous bulk current, the high-angular-momentum topological SC, the gapless nematic SC with quasinematic vestigial phases, which are unigue to the OCs and absent or rare on periodic lattices. Furthermore, we propose an easily realized approach to obtain the long-sought charge-4e sc by using the extrinsic QCs. Our works open the door to study the exotic SCs on QCs.

报告人简介：

杨帆，北京理工大学物理学院教授，博士生导师。2002年博士毕业于北京大学物理学院，2004年从清华大学高等研究中心博后出站，之后加入北京理工大学物理学院。2013年被聘为教授杨帆的主要研究方向为强关联和超导理论。在铜基超导、量子自旋液体、铁基超导、魔角石墨烯、准晶电子态、镍基超导等领域从事研究多年。发表论文70余篇，其中包括11篇Phys. Rev. Lett.和1篇 Nat. Commun.，被引用2500余次。

3 相干电子成像研究进展及应用

报告人：郑长林，复旦大学物理学系

时间：11月12日（周二）10:00

单位：中国科学院物理所

地点：M255 会议室

摘要：

透射电子显微镜是物质科学最重要的微观结构表征工具之一。像差校正技术的发展，结合新一代更高性能及功能更强大的电子显微成像平台, 为凝聚态物质的结构表征提供了卓越的空间分辨率。在本报告中，我们将讨论基于像差校正透射电镜平台，所发展的系列相干电子成像技术，及其在凝聚态物质研究中的应用。我们将讨论利用结构化光阑，实现对相干电子的远场波前调控，并结合电子共聚焦成像技术，实现新型的三维电子成像表征。我们并将讨论对相干电子在固体中的传播及散射的精确模拟，以及原子的关联振动对电子散射的影响，以实现高精度的定量扫描透射成像分析。同时我们还将讨论所发展的新型电子波函数相位恢复与测量技术，及以上技术在半导体材料与器件电场与电势分布测量中的应用。

报告人简介：

郑长林，复旦大学物理学系教授。本科及硕士毕业于南京大学物理系，博士毕业于德国柏林洪堡大学物理系。2010-2017任澳大利亚莫纳什大学电镜中心(MCEM) Research Fellow。2017年底加入复旦大学物理学系，负责双球差校正透射电镜平台的建设与运行，其主要研究方向为发展与应用基于透射电子显微镜的电子散射、成像与谱学分析技术。在Physics Review Letters, Ultramicroscopy, Microscopy, Microscopy and Microanalysis等期刊发表多篇电镜技术发展的论文,两次入选PRL编辑推荐亮点论文。2018年，获澳大利亚显微学会颁发的John Sanders 奖章，以表彰其在电镜技术开发及物理学领域的应用所做出的贡献。

4 Synthesis of elements 119 and 120 with beams heavier than 48Ca

报告人：Tomasz Cap，National Centre for Nuclear Research

时间：11月12日（周二）11:00

单位：中国科学院理论物理所

地点：北楼202

摘要：

The heaviest known element, oganesson, with an atomic number Z=118, was synthesized in a fusion reaction of a 48Ca projectile with a 249Cf target. Californium is currently the heaviest actinide that can be produced in the quantity necessary for superheavy nuclei synthesis reactions. For this reason, the synthesis of new elements must rely on the use of projectiles made from elements heavier than calcium. Currently, various laboratories around the world are developing or have already developed beams of 50Ti, 51V, and 54Cr. These beams can also be used in reactions with lighter actinides to synthesize new isotopes of known elements.

The results and future prospects of selected experiments, particularly the latest efforts aimed at producing elements with atomic numbers 119 and 120, will be presented. Reactions using 50Ti, 51V, and 54Cr beams, which are considered to have the highest probability of success, will be discussed in detail. Calculations of cross sections, performed within the framework of the Fusion-by-Diffusion (FBD) model, will be presented. The FBD model considers the production cross section as the product of three factors: the cross section for the projectile to overcome the entrance channel barrier (capture cross section), the probability that the resulting system fuses and reaches the compound nucleus configuration, and the probability that the excited compound nucleus survives fission during de-excitation.

报告人简介：

Dr. Tomasz Cap obtained his PhD at the University of Warsaw, Poland, under the supervision of Prof. Krystyna Siwek-Wilczyńska. His thesis was dedicated to experimental research on 197Au+197Au collisions at an energy of 23A MeV, with an emphasis on projectile and target-like fragment divisions, reaction dynamics, time scales, and neck fragmentation. The experiments were conducted at INFN LNS in Catania, Italy.

Since 2016, Dr. Tomasz Cap is working at the National Centre for Nuclear Research, Poland, in the theory group established by Prof. Adam Sobiczewski, currently led by Dr. hab. Michał Kowal. The group focuses on the properties and production methods of heavy and superheavy nuclei.

5 先进镁基能源材料开发与应用

报告人：邹建新，上海交通大学材料科学与工程学院

时间：11月13日（周三）10:00

单位：中国科学院物理所

地点：M253会议室

摘要：

镁基材料在储氢和二次电池领域展现出广阔前景。在镁基储氢材料方面，我们采用表面催化、第二相分散等策略，显著改善了材料的吸放氢性能，开发出了一系列高性能镁基储氢材料，并结合原位表征和理论计算研究了镁基复合材料的储氢机理，揭示了界面处的高活性催化相和纳米限域是性能提升的关键。在镁电池正极材料方面，针对Mg²⁺与晶格强静电相互作用导致的扩散缓慢和电化学性能不佳的问题，我们探索了过渡金属硫化物的可行性，并开发了与之匹配的电解液体系，再结合原位同步辐射技术和理论计算，探索了硫化物正极材料储镁的反应机制，为高性能镁电池的设计提供了新的方法和思路。

此外，团队在镁基储能系统的集成与工业应用方面也开展了大量研究工作，成功开发出了全球首辆吨级镁基固态储运氢车，制备出了镁离子软包电池，验证了技术可行性。目前，团队正积极探索更多与镁基储能技术适配的应用场景，为可再生能源利用提供新的解决方案。

报告人简介：

邹建新，上海交通大学材料科学与工程学院特聘教授、教育部长江学者、氢科学中心副主任、国家重点研发计划首席科学家、英国皇家化学会会士、国际先进材料学会会士。主要从事镁基能源材料方面的基础研究与应用开发工作，在Science，Adv Mater等国际知名期刊上发表SCI收录论文180余篇，已授权国内国际发明专利26项，曾获中国有色金属工业技术发明一等奖，国际镁业协会未来技术奖，上海市技术发明二等奖，国际镁科学与技术学会年度人物奖，国际能源署Hydrogen TCP奖等。

6 Active Galactic Nuclei in the Early Universe: Radio Observational Study

报告人：An Tao，中国科学院上海天文台

时间：11月13日（周三）15:30

单位：北京大学物理学院

地点：KIAA-Auditorium

摘要：

Understanding the formation and evolution of the first supermassive black holes remains one of the most intriguing challenges in modern astrophysics. This talk will focus on three key aspects of early universe AGN studies: radio properties of high-redshift blazars and radio-quiet quasars, examining their jet activity and feedback processes; super-Eddington accretion phenomena observed in both early universe and local AGN populations; and studies of dwarf galaxies as local laboratories for understanding first-generation galaxies. Recent multi-wavelength observations and their implications for black hole growth and cosmic evolution will be discussed, highlighting how these complementary approaches help unveil the nature of the earliest active galaxies.

报告人简介：

Dr. Tao An is a senior researcher at Shanghai Astronomical Observatory (SHAO), Chinese Academy of Sciences. He currently leads the prototyping of the Chinese SKA Regional Centre. He serves on various academic committees, including the International Astronomical Union (IAU) Radio Commission and the European VLBI Network (EVN) Proposal Review Committee. With over 200 published papers, his research interests focus on high-resolution observational study of compact objects and radio astronomical techniques.

7 Multidimensional photoemission electron microscopy: Imaging plasmonic fields and beyond

报告人：戴亚南，南方科技大学

时间：11月13日（周三）15:30

单位：中国科学院物理所

地点：M楼236会议室

摘要：

Exploring the realms of physics that extend beyond thermal equilibrium has emerged as a crucial branch of condensed matter physics research. It aims to unravel the intricate processes involving the excitations, interactions, and annihilations of quasi- and many body particles, and ultimately to achieve the manipulation and engineering of exotic non equilibrium quantum phases on the ultrasmall and ultrafast spatiotemporal scales. In this talk, I will first introduce the ultrafast time-resolved photoemission electron microscopy (tr PEEM) technique as a means of studying non-equilibrium physics in condensed matter materials. Next, I will focus on the discussion of the one of the primary applications of tr PEEM, which is the imaging of surface plasmonic responses, including the coherent vectorial imaging of surface plasmon polariton fields and spin textures, spatiotemporal evolution of localized surface plasmons, as well as plasmon-induced hot electron transport in real space. Finally, I will briefly describe our effect in extending tr-PEEM as a multi dimensional probe for studying excited state physics beyond plasmonics.

报告人简介：

Yanan Dai is an associate professor in the department of physics, Southern University of Science and Technology (SUSTech). He obtained his B.S. degree at Shandong University in 2013, and Ph.D degree in physics at the University of Pittsburgh in 2019. Before joining SUSTech in Aug. 2022, he worked as a postdoctoral research scientist in the department of chemistry at the Columbia University. His group at SUSTech now is developing advanced ultrafast optical and photoelectron spectroscopies and microscopies, to achieve multi dimensional detection of excited state dynamics and vectorial Floquet engineering of quantum materials on the nano-femto scales.

8 A Neural Network Approach to Conformal Fields

报告人：田家骅，华东师范大学

时间：11月14日（周四）15:10

单位：北京大学物理学院

地点：物理学院西楼B105

摘要：

In this talk l will present a new way to calculate the conformal correlators. Via embedding formalism we are able to construct conformal fields in d dimension from Lorentz invariant fields in(d+2) dimension. The correlators are calculated via modern amplitude methods. Potential future applications will be discussed. l will be pedagogical as various aspects of the work may be alien to a broad audience.

报告人简介：

Jiahua Tian, professor at Department of Physics, East China Normal University. Before that he was a postdoctoral fellowat KlAS and lCTp. His research focuses on string theory, mathematical physics and Al for physics.

9 Ab initio Charge symmetry breaking interaction and unsolved nuclear structure problem

报告人：Hiroyuki Sagawa，RIKEN&University of Aizu

时间：11月14日（周四）15:30

单位：中国科学院理论物理所

地点：北楼202

摘要：

In my talk, I will present ab initio approach to derive charge symmetry breaking interaction based on quantum chromodynamics (QCD). This Interaction is applied to cure the anomaly in the mass difference of mirror nuclei, known as Okamoto-Nolen-Schiffer (ONS) anomaly, which is an old problem but not yet solved by fully microscopic theory. Our approach is intimately related with the partial restoration of the chiral symmetry breaking in nuclear medium and provides a quantitative solution of the ONS anomaly as the mass difference between protons and neutrons in nuclear medium.

Microscopic approach based on QCD is the most challenging ab initio theory for nuclear structure physics. In this respect, QCD sum rule gives a powerful tool, but numerically not highly demanding, to cross a bridge the QCD and hadron spectroscopy such as meson and baryon masses in terms of spontaneous chiral symmetry breaking due to quark condensation. In nuclear medium, a partial restoration of the chiral symmetry breaking is found in the pionic atom experiments. I will discuss some details of QCD sum rule approach and CSB interaction of nucleon-nucleon (NN) interaction sector.

I will also mention the charge symmetry breaking effect in hyper nuclei which is observed recently.

报告人简介：

Prof. Hiroyuki Sagawa is a theoretical physicist specializing in collective motion in nuclei, spin-isospin excitations, exotic nuclei, charge symmetry breaking in nuclei and hypernuclei. He obtained his Ph.D.in Physics from Tohoku University in 1975, focusing on nuclear theory. He has worked at the University of Tokyo, Utsunomiya University, Niels Bohr Institute, Universié de Paris-Sud, National Institute of Nuclear and High Energy Institute (NIKHEF) at Amsterdam, Michigan State University, and the University of Aizu. Now, he is a Senior Visiting Scientist at RIKEN Nishina Center and a Professor Emeritus at the University of Aizu.

10 透射电子显微学在高温超导和界面超导机理研究中的应用与展望

报告人：王泽朝，南方科技大学

时间：11月15日（周五）14:00

单位：中国科学院物理所

腾讯会议：163-374-936

会议密码：1115

摘要：

高温超导现象自三十多年前被发现以来，由其衍生出的丰富物理现象，对现代凝聚态物理的发展产生了极其重要的影响。2012年发现的单层FeSe/SrTiO3界面超导为高温超导的研究提供了新的契机。然而，无论是高温超导体还是界面超导体，都因其复杂的晶格结构和量子多体相互作用，其超导态产生的微观机理是公认的科学难题，至今依然不完全清楚。如何从亚原子尺度去理解和探测铜氧化物高温超导体和界面超导体的微观量子序参量（包括点阵序、电荷序、轨道序、自旋序和拓扑序）将为理解高温超导机理提供非常重要的启发。本报告将讨论基于先进的电子显微学及其发展而来的新方法，总结近年来利用透射电子显微镜在高温超导和界面超导机理研究中的最新进展，并重点讨论了其在铜氧化物高温超导体中对赝能隙态下的拓扑磁结构的发现(Nature, 615, 405-410, 2023)，电荷转移能隙与最大超导转变温度的关系(Science, 381, 227-231, 2023)和晶格-声子相互作用等方面取得的最新研究进展，最后给出了透射电子显微学在高温超导和界面超导机理研究中的未来展望。

报告人简介：

王泽朝博士，2023年6月于清华大学获博士学位，导师为：朱静院士，2023年8月至今，在南方科技大学物理系开展博士后研究，合作导师为：薛其坤院士。主要的研究兴趣是利用先进的电子显微镜(透射电镜和扫描隧道显微镜)及其发展出的多种电子显微学方法，在实空间，原子和亚原子尺度，直接探测复杂高温超导材料体系和界面超导体系中的点阵、电荷、自旋、轨道和拓扑等基本序参量，以揭示与高温超导机理有关的重要谜题。近年来，以第一作者身份在Nature, Science和Nature Materials发表相关论文3篇。2024年至今，主持国家自然科学基金青年项目，入选2024年度博士后创新人才支持计划。

封面图片来源：https://zhuanlan.zhihu.com/p/625294510

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