交错磁性、二维磁性材料、大自旋轨道耦合系统、过冷液体 | 本周物理讲座

报告人： 杨诗祺，北京大学

时间：7月4日 (周二) 14:00

单位：中科院物理所

腾讯会议：679 173 664

密码：98417

摘要：

磁性材料是研究自旋电子学器件和量子器件的材料基础。二维磁性材料由于其原子级薄的厚度和在二维极限下仍保持新奇的物理化学性质成为完善基础磁学模型和实现小型化信息存储器件的关键候选材料。在本征二维磁性材料及其磁调控基础上，将磁性与拓扑性质的结合将进一步拓宽磁学体系及量子信息领域的研究和发展。因此，本报告主要针对MnBi2nTe3n+1 (n=1, 2, 3) 和 CrX3 (X=Cl, I, Br) 两种二维磁性材料体系，研究其从三维到二维极限下的磁性及其磁调控，并探寻微观机理，为设计制备新型自旋电子器件提供理论指导和实验支持。

报告人简介：

杨诗祺博士分别于2018年获得电子科技大学学士学位，2023年获得北京大学博士学位，并获评北京大学优秀博士学位论文奖。2023年7月开始在北京大学物理学院开展博雅博士后研究，合作导师为叶堉副教授。近五年来以第一/共一作者身份在Physical Review X (1), Nature Communications (2)等国际知名期刊发表相关论文4篇，并有三篇一作/共一文章待发表。其中，高被引论文2篇，H因子9。曾多次参加国际会议作出口头报告/墙报并获奖项。

报告人：Jinwu Ye，Great Bay University/Mississippi State University

时间：7月4日 (周二) 15:00

单位：中科院物理所

地点：M830

摘要：

Despite the special theory of relativity was discovered ABOUT 120 years ago, how the temperature transforms in the theory remains unknown. This historical outstanding problem was initiated from the phenomenological thermodynamics point of view by the late giants such as  Planck, Einstein, Pauli and Laue and also followed  intensively by many other people. Here we resolve this outstanding problem by using a completely different approach: writing a partition function  in terms of  path integral in the imaginary time at a finite temperature,then perform Lorentz transformation directly on the partition function. The most disruptive change from the temperature $ T=0 $ to $ T > 0 $ is the existence of a reservoir which sets up the temperature and the chemical potential. Then the original bi-partite problem of the System + Observer at $ T=0  $ becomes a trinity problem of the Reservoir + System + Observer. It is the relative motion between the system and the reservoir which dictates the Law of Temperature Transformation. We also study the effects of a finite chemical potential and the low energy limit leading to condensed matter systems. Impacts on the thermodynamic zeroth to the third laws are given. Contrast to the Unruh effects for an accelerating observer are made. Possible implications on the thermodynamics of a quantum black hole are hinted through the AdS/CFT correspondence. Feasible experimental detections of these effects in the condensed matter systems are analyzed. Our mathematical derivation is simple, physical picture is transparent,the philosophical view of the space, time and temperature as the three most fundamental quantities of the universe is appealing.

报告人：Yinming Shao (邵垠铭), Columbia University

时间：7月4日 (周二) 16:00

单位：清华大学物理系

地点：理科楼C302

摘要：

The discovery of nodal-line semimetal ZrSiS extends the notion of Dirac fermions from points to lines and loops in the momentum space. Identifying new nodal-line fermions is challenging since often the Dirac nodal-lines are dispersive, submerged within a Fermi sea, and gapped by spin-orbit-coupling. I will first introduce how precise power-law behavior of the optical response function can reveal the hidden nodal-line fermions, using NbAs2 as an example. The large anisotropy associated with nodal-line structure gives rise to greatly reduced kinetic energy along the line. I will discuss the two fundamental spectroscopic hallmarks of electronic correlations observed in ZrSiSe: strong reduction (1/3) of the free carrier Drude weight and of the Fermi velocity renormalization compared to predictions of density functional theory. Another consequence of the nodal-line structure is the large difference in the plasma frequencies for in-plane and out-of-plane responses, leading to a broadband hyperbolic regime covering infrared and visible frequencies. I will show our recent observation of propagating hyperbolic waves in ZrSiSe, enabled by the van Hove singularities in the nodal-squares. Finally, I will discuss our recent effort in isolating surface and bulk electrodynamics in Weyl semimetals based on near-field photocurrent imaging at the nanoscale. Our tip-based approach circumvents the diffraction limit and surface- and bulk-related nonlinear contributions are distinguished through their “symmetry fingerprints” in the real-space nano-photocurrent maps.

报告人简介：

邵垠铭博士于2009-2013本科就读于浙江大学。先后于加州大学圣地亚哥分校（2013-2016）和哥伦比亚大学（2017-2019）攻读物理学博士学位。2020至今于哥伦比亚大学从事博士后研究。

报告人：张新民，中科院高能所

时间：7月5日 (周三) 16:00

单位：清华大学物理系

地点：理科楼郑裕彤大讲堂

摘要：

阿里原初引力波探测实验(AliCPT)是我国首个宇宙微波背景辐射(CMB)极化实验，具有高海拔(5250米)、高灵敏度、北半球唯一的特点。本报告将首先简介AliCPT的实验进展；然后介绍AliCPT相关的科学，包括暴涨与宇宙起源理论，原初引力波与引力量子化，AliCPT与Chern-Simons理论，AliCPT毫米波巡天科学等;最后介绍国际原初引力波探测和CMB实验发展趋势及AliCPT发展规划。

报告人简介：

张新民，高能所研究员，阿里原初引力波探测实验首席科学家/AliCPT国际合作组发言人。1991年美国洛杉矶加州大学(UCLA)物理和天文系研究生毕业获博士学位，1996年回国在高能所工作至今。1997年入选中科院百人计划，1999 年获国家级人才基金资助，2004年当选《新世纪百千万人才工程国家级人选》。2021年被聘为科技部国家重点研发计划“引力波探测”重点专项实施方案编制专家组专家、总体专家组副组长。

报告人：寇煦丰，上海科技大学

时间：7月6日 (周四) 14:00

单位：中科院物理所

地点：M楼238会议室

摘要：

In order to address current challenges of spintronics, opportunities may exist for a focus research on the understanding and manipulation of fundamental spin-orbit coupling (SOC) in topological quantum materials. In this talk, I will present our work on the control of spin/magnetic states in magnetic topological insulators-based heterostructures. The independent manipulation of the topology of energy band and the magnetic exchange order enable us to observe emerging effects towards higher temperatures. In addition, I will also summarize our work on utilizing interfacial Rashba SOC in lattice-matched InSb/CdTe heterostructures for realizing gate-tunable non-reciprocal charge transport and spin-orbit-torque-based magnetization switching with highly spin-to-charge conversion efficiency at room temperature. Our work may help construct a wide range of ultralow-power spin？orbitronics applications.

报告人简介：

Dr. Xufeng Kou received his BS degree (with honor) in Chu Kochen Honors College from Zhejiang University (2009). From 2009 to 2015, he received his MS and PhD degrees in Electrical Engineering from UCLA. Since February 2016, he joined the School of Information Science and Technology at ShanghaiTech University. So far, Dr. Kou has published 3 book chapters, and co-authored 90 peer-reviewed journal/conference papers including Nature Electronics, Nature Materials, Nature Nanotechnology, Nature Communications, Physical Review Letters, and IEEE IEDM. with more than 900 citations (h-index of 36). He also holds several awards including the Qualcomm Innovation Fellowship (2012), Chinese Outstanding Student Abroad Scholarship (2013), Distinguished PhD Dissertation Award of UCLA (2015), Shanghai May 4th Youth Medal (2018), Shanghai 35U35 Award (2021), and Shanghai Pudong Elite Researcher Award (2023).

报告人：池震栋，巴斯克纳米科学合作研究中心

时间：7月6日 (周四) 14:00

单位：中科院物理所

地点：怀柔园区MA楼505会议室

腾讯会议：399-873-770

会议密码：0706

摘要：

With the remarkable expansion of IT industry, the increasing energy consumption associated with traditional CMOS technology has emerged as a significant obstacle impending its further development. Spintronics is a field of study with potential application for future non-volatile memory and logic devices. By utilizing spin current instead of charge current, spintronics enables significantly lower energy consumption, making it a promising candidate for beyond-CMOS technology. Currently, the focus in spintronics lies on the charge-spin interconversion (CSI), which enables the switching of magnetic element by electrical current, essential for magnetic random-access memories (MRAM). The control of CSI offers opportunity for designing advanced multifunctional devices with broader applications. Graphene-based van der Waals heterostructures is an intriguing platform for investigating the tunable CSI due to their high electronic/structural tunability. In this report, I would like to introduce two of my recent studies on the tunable CSI in graphene-based van der Waals heterostructures. The first study explores graphene/1T-TaS2 heterostructures, where 1T-TaS2, a transition-metal dichalcogenide, exhibits various charge-density wave (CDW) phases. We observe the CSI can be turned ON and OFF by manipulating the CDW phases in 1T-TaS2. The second study focuses on graphene/heavy metal heterostructures, where we discover that the deposition of heavy metal onto graphene serves as a general method to enhance the CSI efficiency on graphene. Additionally, the CSI efficiency can be finely controlled by using a gate voltage.

报告人简介：

池震栋，西班牙CIC nanoGUNE BRTA（巴斯克纳米科学合作研究中心）博士后。2015年本科毕业于南京师范大学物理系。2018年和2021年于日本东京大学分获理学硕士和理学博士学位。博士学位在读期间主要对半金属铋及其拓扑绝缘体化合物的电荷-自旋转换性质进行了系统性的研究，证实了其由狄拉克电子引起的巨大体态自旋霍尔效应。2021年4月起于nanoGUNE开展博士后工作，主要从事低维材料的器件加工，以探索其自旋电子学、量子输运等新奇物理特性。于Science Advances, Phys. Rev. Lett., Nano Lett., Phys. Rev. B, Phys. Rev. Research等国际著名刊物发表论文19篇。

报告人：Jinwu Ye，Great Bay University/Mississippi State University

时间：7月6日 (周四) 15:00

单位：中科院物理所

地点：M830

摘要：

Poincare and Einstein’s special relativity says that any physics law in a vacuum takes identical form in any two inertial frames. On the opposite direction, P.W. Anderson’s " More is different " says that various  macroscopic quantum or topological phenomena emerge in a material which contains enormous number of interacting particles. In contrast to the relativistic quantum field theory, there is always a reservoir which can exchange energy and the particles with a material. It remains an outstanding problem to apply Einstein’s special relativity to  Anderson’s " More is different ". Here we address this outstanding problem and find that the combination leads to many new effects. We demonstrate these new effects by studying one of the simplest quantum phase transitions (QPT): Superfluid (SF)-Mott transitions of interacting bosons in a square lattice  in a sample moving with a constant velocity. The Lorentz transformation just reduces to the Galileo transformation in the speed of light $ c o infty $ limit. It is the moving which mixes the space and time, then leads to the emergent space-time near the QPT. It is the existence of reservoir which makes crucial differences between a moving sample and a moving inertial frame. We also stress the important roles played by the underlying lattice. The experimental detection of these dramatic new effects in some materials or cold atoms loaded in an optical lattice are discussed.

报告人：宋成，清华大学

时间：7月6日 (周四) 16:00

单位：南方科技大学物理系

链接： https://www.koushare.com/lives/room/743098

摘要：

交错磁性（altermagnet）兼具铁磁自旋能带劈裂的特点和反铁磁无净磁矩且本征频率高的优势，是自旋电子学领域最新的研究热点之一。本报告讲述一类典型的交错磁体RuO2中的实验研究结果，包括自旋劈裂力矩（spin splitting torque）效应及其逆效应。首先，我们基于自旋力矩铁磁共振技术实验发现了交错磁自旋劈裂效应媒介的电荷自旋转化过程，其产生的自旋流不依赖于自旋轨道耦合且极化方向受RuO2奈尔矢量的调制，为实现可控自旋流打开了新思路。通过设计倾斜的奈尔矢量，实现观察到了面外自旋极化产生，并进而诱导自旋劈裂力矩以实现垂直磁化的无外场辅助翻转。此外该自旋劈裂力矩可兼具传统自旋转移力矩极化方向可控和自旋轨道力矩器件耐受性强的优势。其次，基于自旋塞贝克实验，我们观察到了RuO2薄膜中奈尔矢量调制的自旋电荷转化过程，以此实现了对不同极化方向自旋流的探测。基于上述新机制，我们构造了RuO2/Py异质结构型，实现了振幅和偏振方向可调的自旋太赫兹源。除了RuO2，我们还将交错磁体的实验探究推广到其他材料体系（Mn5Si3和CrSb），观察到了大的反常霍尔和反常能斯特效应，并以此为探测手段探究了对其磁矩的电学操控。上述对交错磁体的实验探究不仅为基础磁学研究带来崭新的视角，更将为自旋电子学的器件应用注入新活力。

报告人简介：

宋成，博士，清华大学长聘教授，国家杰出青年科学基金获得者。研究方向为信息功能材料，主要包括自旋电子学材料、声表面波滤波器和磁电/声电耦合器件。在Nature Materials和Nature Electronics等期刊发表学术论文200余篇，论文被引用约12000次。曾获2012年度国家自然科学奖二等奖、2018年度国家科技进步奖二等奖和四项省部级科技奖励。兼任中国材料研究学会常务理事/青委会主任、中国真空学会理事/薄膜专委会副主任。

报告人：Qi Zhou，Purdue University

时间：7月7日（周五）10:00

单位：中科院物理所

地点：M830

摘要：

Many quantum non-Hermitian phenomena appear peculiar compared to their Hermitian counterparts.  I will discuss an unprecedented  duality between non-Hermiticity and curved spaces, which provides a natural explanation for fundamental non-Hermitian phenomena including but not limited to non-orthogonal eigenstates, non-Hermitian skin effects and the sensitivity to boundary conditions. This duality offers experimentalists a new means to explore curved spaces without physical distortion. Alternatively, curved spaces could be used to study non-Hermitian physics without resorting to dissipation. 

报告人简介：

Qi Zhou is a professor in the Department of Physics and Astronomy at Purdue University. His research interests include synthetic gauge fields for ultracold atoms, strongly interacting bosons and fermions, quantum nonequilibrium dynamics, and connections between few-body and many-body physics. Qi Zhou received his Ph.D. degree from The Ohio State University and his B.S. degree from Tsinghua University, China.

报告人：Hajime Tanaka，The University of Tokyo

时间：7月7日（周五）15:00

单位：中科院理论物理所

Zoom会议号：823 9391 0448

密码：780523

摘要：

The fate of a liquid, whether it crystallizes or vitrifies, is determined by the cooling rate, but the underlying physical factors influencing this outcome have remained unclear. As a liquid is cooled, the development of structural order occurs to minimize the system’s free energy. In the case of fragile liquids, we have discovered that the growth of static structural order leads to slow glassy dynamics. However, detecting this structural ordering is challenging since it arises from many-body correlations and is not easily observed using two-body density correlators, unless it involves translational ordering, such as the formation of tetrahedral structures in materials like silica and water. Structural ordering acts as a precursor for crystal nucleation and plays a crucial role in selecting polymorphs when it aligns with crystal symmetry. Additionally, we have examined the glass-forming ability of systems with competing orderings and observed that the enhancement of glass-forming ability arises from an increased contrast in structural properties between the liquid and crystal phases. These findings collectively suggest that the development of structural order in supercooled liquids governs slow glassy dynamics, crystallization, and the ability to form glassy materials.

报告人简介：

Prof. Hajime Tanaka obtained his Ph.D. from the University of Tokyo in 1982. After graduation, he became an assistant professor at Prof. Nishi’s Lab., the University of Tokyo. He was promoted to full professor at the Institute of Industrial Science in 1999, the University of Tokyo and held several positions as visiting scientist at AT & T Bell Laboratory and Rutgers, Cavendish Lab., etc. He received the Award of the Society of Polymer Science, Japan in 2007, and top paper awards from J. Phys.: Condens. Matter in 2004, 2005, 2006 as well as the Liquid Crystal Society in 2010. He won Humboldt Research Award (Alexander von Humboldt Foundation, Germany) in 2006 and was elected as a fellow in the Institute of Physics in 2007.

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