镍氧化物高温超导、锂电正/负极、自旋流—电荷流转换 | 本周物理讲座

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报告人：楼宇庆，清华大学

时间：6月4日（周二）12:00

单位：中国科学院理论物理研究所

地点：南楼6620

摘要：

我们分别介绍与磁化超大质量恒星（Magnetized Supermassive Stars)、绝超质量黑洞(Hypermassive Black Holes)、磁化相对论脉冲星风(Magnetized Relativistic Pulsar Winds)等相关的物理图像、模型分析、理论预言、主要结论和侦测手段并探讨一系列可能的天体物理和宇宙学相关后果。

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报告人：张广铭，清华大学物理系

时间：6月5日（周三）10:00

单位：中国科学院物理研究所

地点：M236会议室

摘要：

镍氧化物超导是近几年新发现的非常规超导体系，分别为Lnn+1NinO3n+1和Lnn+1NinO2n+2钙钛矿结构，其中Ln代表稀土元素La、Pr、Nd等。2019年，美国科学家首先在Nd1-xSrxNiO2薄膜中发现超导电性，但超导转变温度仅有15 K，压力下也没有超过40 K。2023年，中国科学家在双层镍氧化物La3Ni2O7单晶材料中，通过施加高压发现接近80 K的高温超导电性(Sun,et.al.,Nature621,493)。镍氧化物La3Ni2O7材料体系的基本特征为：Ni为+2.5价，dz2轨道接近半满，dx2-y2轨道接近1/4占据，完全不同于铜氧高温超导体中Cu2+的半满dx2-y2电子结构。根据这些独特结构，我们首次提出了一个包含dx2-y2和dz2轨道电子的双层有效微观模型，并明确指出层间的dz2轨道电子通过顶点氧形成σ和反σ键能带，而局域的电子库伦排斥相互用将导致一个层间on-site反铁磁海森堡自旋耦合。在高压下，强的层间on-site反铁磁海森堡自旋耦合导致dz2轨道电子配对，通过与巡游的dx2-y2轨道电子的杂化，产生非常规超导电性。为此，我们还提出了一个双层镍氧化物超导的两分量理论，该理论代表了一种新的配对机制，揭示了双层镍氧化物高温超导和铜氧化物高温超导的本质区别，对建立普适的高温超导微观机理具有重要意义。

报告人简介：

张广铭教授，1991年获上海交通大学凝聚态物理学博士学位，先后在意大利国际理论物理中心（ICTP）和伦敦帝国理工大学任研究助理。1997年，任清华大学高等研究中心研究员，2004年至今,任清华大学物理系教授，现任清华大学凝聚态物理研究所所长和低维量子物理国家重点实验室副主任。长期研究凝聚态物理学中的量子多体问题，提出严格求解二维Kitaev量子自旋模型的新方法；建立二维量子数分数化激发的统一理论；构建一维量子整数自旋链拓扑态的普适类；发展关联电子多体系统中近藤共振和磁性关联的量子多体理论；与实验组合作，首次发现液氮温区镧镍氧La3Ni2O7压力下非常规超导电性。1999年获香港求是科技基金会“杰出青年学者”奖，2001年获“国家杰出青年基金”资助，2006年被教育部聘为“长江学者特聘教授”，2011年获中国物理学会“叶企孙物理奖”。

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报告人：王春阳，中国科学院金属研究所沈阳材料科学国家研究中心

时间：6月5日（周三）10:00

单位：中国科学院物理研究所

报告地点：怀柔园区EA楼311会议室

腾讯会议：598-942-276

会议密码：2024

摘要：

先进透射电子显微术（TEM）是揭示电池材料工作/失效机制和构效关系不可或缺的强大表征手段。随着计算机技术、微纳加工技术和人工智能技术的迅猛发展，多维（原位+三维）透射电镜技术近年在电池材料研究中发挥了巨大作用。在本报告中，我将重点汇报我们利用人工智能TEM技术和多维TEM技术在锂电池正极、负极和电解质材料构效关系研究中取得的进展。主要内容包括：1）锂电层状氧化物正极材料的相变退化与力学失效机理；2）锂金属形核、生长与剥离机制；3）固态电解质中的锂离子传输机制与失效机理等研究进展。

报告人简介：

王春阳，中国科学院金属研究所沈阳材料科学国家研究中心研究员、博士生导师。于2019年从中国科学院金属研究所获得博士学位，随后在2019年至2023年期间在加州大学欧文分校和布鲁克海文国家实验室从事博后研究。他的主要研究方向是先进原位透射电镜技术、电子层析技术和冷冻透射电镜技术的发展，及其在金属、电池材料研究中的应用。目前已发表研究论文60余篇, 其中以第一/共一/通讯作者在Nature、Nature Materials、Nature Energy、PRL、Matter、Advanced Materials、EES、Angewandte Chemie、Nano Letters、ACS Energy Letters等期刊发表论文20余篇。2022年获美国电子显微学会MSA Postdoc Scholar Award，担任M&M2020电镜三维成像分会主席。受邀担任布鲁克海文国家实验室功能纳米材料中心提案评审委员会委员、用户委员会委员。担任材料领域期刊JMST青年编委以及ACS Nano等十余种国际学术期刊审稿人。受邀在M&M、ECS、TMS、BNL Users’ Meeting、ICEnSM等国际会议作邀请或口头报告10余次。

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报告人：张警蕾，中国科学院合肥物质科学研究院强磁场科学中心

时间：6月5日（周三）11:00

单位：中国科学院物理研究所

报告地点：怀柔园区X1南楼101会议室

腾讯会议：435-881-125

会议密码：2024

摘要：

稳态强磁场实验装置是一个针对多学科实验研究需要的极端实验条件设施。依托于稳态强磁场装置，我们发展了各类输运物性表征系统，可以在最强磁场45.22T，最低温度0.3K的综合极端条件下实现对材料电、热、磁等多种物理性质的高精度测量。报告的第一部分将对这些测试系统的测量原理进行阐述，展示在关联电子材料研究中的应用。报告第二部分主要聚焦于理想一维外尔半金属相反常热电响应的研究。外磁场下，三维拓扑绝缘体中准连续的电子态会量子化为一系列分立的朗道能级，仅在平行磁场方向上仍保持色散。弱拓扑绝缘体自旋极化的第零朗道能级在足够强的磁场下可以形成理想一维外尔模。我们研究了弱拓扑绝缘体HfTe5在强磁场下的塞贝克和能斯特效应，探测第零朗道能级在量子极限下的拓扑相变，给出理想一维外尔相的输运实验证据。

报告人简介：

张警蕾，中国科学院合肥物质科学研究院强磁场科学中心研究员，博士生导师。2014年毕业于浙江大学物理系，同年加入强磁场科学中心。依托于稳态强磁场大科学装置，设计和搭建了一系列独具特色的物性测试系统，实现了在强磁场（>30T）下对材料电、磁、热等多类物性的测量。利用这些技术，聚焦于拓扑量子材料、非常规超导等关联电子体系强磁场下输运性质的研究，以主要作者在NatureMaterials，NaturePhysics，Phys.Rev.Lett.等期刊发表论文20余篇。2021年获国家自然科学基金优秀青年项目资助；2022入选中科院青促会优秀会员；2024年获第七届马丁•伍德爵士中国物理科学奖。

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报告人：缪冰锋，南京大学物理学院

时间：6月5日（周三）15:00

单位：中国科学院物理研究所

地点：M253会议室

摘要：

自旋流—电荷流转换能够实现自旋流的产生与探测，是自旋电子学研究的重点问题。多种机制可以实现自旋流与电荷流的相互转换，例如：界面Rashba-Edelstein效应、体的自旋霍尔效应、交错磁体中的自旋劈裂效应等。这些效应具有十分类似的表现形式，对相关物理现象背后机制的判别一直是本领域的难点和争论点。本报告将介绍自旋泵浦效应及自旋塞贝克效应两种产生纯自旋流的方法，并报道我们在Ag/Bi体系、磁性金属Co/Pd多层膜、Py单层膜、潜在的交错磁体RuO2中的自旋流—电荷流转换研究。基于对称性分析，我们的主要结论如下：1、Ag/Bi或者Bi与铁磁金属的界面存在较强的Rashba-Edelstein效应，而Ag/Bi界面本身的Rashba-Edelstein效应较弱；2、磁性金属可以产生共线的自旋流，其自旋极化方向与自旋流或者电荷流方向平行，基于共线自旋流能够实现垂直磁矩的无场翻转；3、RuO2体系中的自旋流—电荷流转换主要源自各向异性的自旋霍尔效应，而自旋劈裂效应的贡献较小。我们的结果提供了辨别不同自旋流—电荷流转换机制的方法，也澄清了在相关体系中的争论。

报告人简介：

缪冰锋，南京大学物理学院教授、博士生导师。2009年于南京大学取得学士学位，2012年至2013年在约翰霍普金斯大学交流学习，2014年于南京大学取得博士学位。一直从事自旋流相关研究，以主要作者发表论文20余篇，包括Phys. Rev. Lett. 3 篇，Sci. Adv. 1 篇，Nat. Commun. 1篇，Phys. Rev. B 9 篇等，论文他引1200余次。

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报告人：杨鲁懿，清华大学

时间：6月6日（周四）10:00

单位：中国科学院物理研究所

地点：M253会议室

摘要：

Magnetic topological materials not only exhibit novel exotic quantum phenomena like the quantum anomalous Hall effect but also hold promise for various applications, including information storage and dissipationless transport. In this talk, I will discuss our recent ultrafast studies of spin dynamics in two types of magnetic topological materials using time-resolved optical techniques.

In the first part, we report a systematic investigation of ultrafast magnetization and coherent magnon dynamics in few-layer MnBi2Te4, a novel magnetic topological insulator, as a function of layer number, temperature and applied magnetic field. Below the Neel temperature, we observe laser-induced magnetization processes that can be used to accurately track the distinct magnetic states in different magnetic field regimes, including showing clear odd-even layer number effects. In addition, strongly field-dependent antiferromagnetic magnon modes with tens of gigahertz frequencies are optically generated and directly observed in the time domain. These measurements pave the way for potential applications in 2D antiferromagnetic spintronics and magnonics as well as further studies of ultrafast control of both magnetization and topological quantum states.

In the second part, we study coherent magnon dynamics in topological kagome ferromagnet Co3Sn2S2. To our surprise, we directly observed two magnon modes in the terahertz range in the time domain for the first time. This marks the highest magnon resonance frequencies ever reported in ferromagnets. Supported by a microscopic model, we propose that these dual modes emerge from the low-energy collective excitations of coupled spin and orbital magnetic moments in the presence of ferromagnetic long-ranger order on the kagome lattice. Therefore, our work uncovers a novel type of magnons due to orbital magnetic moments and lays the foundation for the development of terahertz spintronic devices using topological kagome ferromagnets.

报告人简介：

Prof. Luyi Yang received her B.S. in physics and mathematics from Tsinghua University (2007). She earned her Ph.D. in physics from the University of California at Berkeley (2013). Then she worked as a Los Alamos Director’s Postdoctoral Fellow at the National High Magnetic Field Laboratory at Los Alamos. She became an Assistant Professor at the University of Toronto in 2016. She joined the Department of Physics, Tsinghua University as an Associate Professor in September 2019. She was awarded Canada Research Chair, CIFAR Global Scholar and Young Thousand Talents. Her research interests focus on the development of novel optical spectroscopies and their application to problems at the forefront of condensed matter and materials physics.

7

报告人：Prof. Manqi Ruan，IHEP，CAS

时间：6月6日（周四）14:00

单位：北京大学物理学院

地点：物理学院西B105

摘要：

The Circular Electron Positron Collider, proposed right after the Higgs discovery, is one of these electron positron Higgs factories. In the latest design, it is expected to deliver 4 million Higgs bosons, hundreds of Millions of W bosons, 4 Tera Z bosons, and potentially also 1 million top quarks in an extremely clean collision environment. The CEPC could well be the gateway towards the propound physics principles underneath the Standard Model, and possibly shed light on many of the profound mysteries, including the origin of mass, the origin of matter, and the nature of dark matter. The reconstruction, especially the reconstruction towards the hadronicsystem, is critical for the science at electron positron Higgs factory. This talk presents two corner stones of CEPC reconstruction, the Particle Flow that pursues the 1-1 correspondence between reconstructed particle and final state particles, and the jet origin identification that aims to identify the origin quark or gluon that cascade into jets. The impact of those tools on the physics is also discussed.

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报告人：Rixin Li，加州大学伯克利分校

时间：6月6日（周四）15:30

单位：北京大学物理学院

地点：KIAA-Auditorium

摘要：

The first step in planet formation is to build planetesimals from dust particles in protoplanetary disks. The origin and demographics of planetesimals are crucial to understanding the Solar System, exoplanetary systems, and circumstellar disks. In this talk, I will present our latest works on planetesimal formation via the streaming instability, a mechanism to aerodynamically concentrate dust particles and produce planetesimals. I will also discuss the implications and connections between our high-resolution simulation results and recent disk observations, as well as Solar System explorations.

报告人简介：

Dr. Rixin Li is a 51 Pegasi b Postdoctoral Fellow at the University of California, Berkeley. His research uses computational simulations to understand the evolution of dusty protoplanetary disks, the formation of planets therein, and the evolution of black holes embedded in AGN disks. Based on these calculations, he makes observable predictions to test the underlying theories. Dr. Li received his B.S. in Astronomy from Peking University, Ph.D. in Astronomy and Astrophysics from the University of Arizona, and was a postdoc at Cornell University.

9

报告人：张远波，复旦大学

时间：6月6日（周四）16:00

单位：清华大学物理系

地点：理学院郑裕彤大讲堂

摘要：

Two-dimensional (2D) atomic crystals, best exemplified by graphene, have emerged as a new class of material that may impact future science and technology. From a material physicist's point of view, 2D materials provide vast opportunities on two fronts. First, the reduced dimensionality in these 2D crystals often leads to novel material properties that are different from those in the bulk. Second, the entire 2D crystal is a surface, so it is possible to have better control of their material properties with external perturbations. In this talk I will illustrate these two points with examples. In particular, few-layer MnBi2Te4 is an intrinsic magnetic topological insulator, and its superior material quality has recently enabled us to observe the quantum anomalous Hall effect; we are also able to exfoliate high temperature superconductor Bi2Sr2CaCu2O8+d down to monolayer. We explore their electronic properties while the doping and dimensionality of the 2D systems are modulated.

报告人简介：

Yuanbo Zhang obtained his Bachelor's degree from Peking University in 2000 and completed his PhD in Physics at Columbia University in 2006. He served as a Miller Research Fellow at the University of California, Berkeley, from September 2006 to June 2009, and later worked as a postdoc research associate at IBM Almaden Research Center from March 2010 to September 2010. Since 2011, Yuanbo Zhang has been a professor at Fudan University. His research focuses on electronic transport in two-dimensional materials, and he also utilizes a scanning tunneling microscope to probe these materials at the atomic scale.

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报告人：刘家臻，清华大学

时间：6月7日（周五）15:30

单位：中国科学院理论物理研究所

地点：南楼6620

摘要：

The dynamics of complex networks have recently received much attention, with many applications in social, biological, and technical systems. Empirical studies suggest that coevolving dynamics, the interplay between network evolution and nodal dynamics, is responsible for many important phenomena in complex networks. Here, we present two concrete examples of the coevolving dynamics in complex networks.

For complex social systems, polarization is a ubiquitous phenomenon. We proposed a coevolving framework that counts for opinion dynamics and network evolution simultaneously from the perspective of statistical physics. Under a few generic assumptions on social interactions, we found a bi-polarized community structure emerges naturally from the coevolving dynamics. Our analytical result predicts a depolarization/polarization phase transition, in line with empirical observations. For human-AI interaction systems, recent years have witnessed that AI-driven recommendation algorithms lure the system into information homogeneity, in which individuals are isolated from diverse information and eventually trapped in a single topic or viewpoint. We derive a mechanistic model for the coevolving information dynamics in complex human-AI interaction systems. This allows us to unearth basic mechanisms underlying the information homogeneity theoretically. These two examples demonstrate how coevolving dynamics drive the emergence of complex network structures and non-trivial phenomena from simple mechanisms.

报告人简介：

刘家臻，清华大学水木博士后、清华大学电子工程系张克潜冠名博士后。本科毕业于山东大学空间科学与物理专业，导师为姜云国教授。博士毕业于美国迈阿密大学（University of Miami）物理专业，导师为Chaoming Song教授。研究方向为统计物理，侧重于复杂系统和复杂网络理论以及相关交叉学科中的应用研究。科研成果发表在Physical Review Letters、Nature Machine Intelligence、Chinese Physics C等期刊上。其研究成果被Nature Machine Intelligence、Physics Today公开报道。

图片来源于：https://www.cnblogs.com/joyfulphysics/p/4779943.html

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