晶体几何及其拓扑不变量、非常规费米表面、质子电荷半径、多体物理 | 本周物理讲座

1

报告人：Tilman Schwemmer，Wuerzburg University

时间：5月30日（周二）10:30

单位：中国科学院理论物理研究所

地点：南楼6620

摘要：

Already at the level of weak coupling, electronic correlation effects beyond single particle propagator renormalization can trigger Fermi surface instabilities such as itinerant magnetism, charge density wave phases, superconductivity, or other symmetry broken states of matter. In this talk, I will present our functional and weak coupling renormalization group studies for electronically driven spontaneous symmetry breaking in two experimentally relevant systems.

The first half of the talk concerns the half-Heusler semimetal and superconductor LuPtBi, where both SOC and electronic correlation effects are prominent, and thus indispensable for any concise theoretical description. The metallic and weakly dispersive surface states of this material feature spin momentum locked Fermi surfaces, which we propose as a possible domain for the onset of unconventional surface superconductivity.

In the second half part we will focus on the extended Kagome Hubbard model as a theoreticians first avenue to interpret experimental results in the recently discovered Kagome metals AV3Sb5. The Kagome sublattice structure of corner sharing triangles, even in a most simplistic single orbital abstraction, already gives rise to an intricate composition of Fermi level eigenstates resulting in the promotion of longer range interactions. In addition to the rich phase diagram of this model, our most recent calculations identify a pair density wave instability in the Kagome Hubbard model, thereby providing a microscopic setting for PDW in a controlled limit.

2

报告人：李阁平，中国科学院金属研究所

时间：5月30日（周二）14:00

单位：中国科学院物理研究所

地点：D210会议室

摘要：

费米面是晶体空间的拓扑曲面，等价于正空间的电子云连通曲面。钛、锆、铪金属由BCC到HCP，HCP到FCC相变的拓扑不变量是密排面点群。塑性变形中全位错的位错芯可定义为亏格，拓扑流形由球面变为环面，位错组合是环面连通和，塑性变形的拓扑不变量是曲面可定向性。

报告人简介：

李阁平，中国科学院金属研究所研究员、博士生导师。于1995年在中国科学院金属研究所获得博士学位，2003年国家公派赴美国高级访问学者，回国后在中国科学院金属研究所钛合金研究部工作至今。研究涉及钛、锆、铪、铼，氧化碲、碲化铋、铅铋材料。科研工作是建立晶体结构与材料力学性能通道，寻找晶体几何变换过程的不变量。在Acta Materialia、Scripta Materialia、Nanoscale等期刊发表论文100余篇；授权专利30余项。

3

报告人：吴从军，西湖大学

时间：5月30日（周二）14:00

单位：中科院物理研究所

地点：M楼253会议室

直播链接：

摘要：

Mean-field theories for many-body states rely on two-fermion orderings. Order parameters lie in either the particle-particle channel such as pairing orders for superconductivity, or, in the particle-hole channel such as spin-density-wave orders for antiferromagnetism. We examine this class of multi-particle fermion multi-particle clustering instabilities in one-dimensional spin-3/2 fermion systems via the renormalization group and bosonization method, which exhibit the quartetting superfluidity (charge 4e) and quartet density wave orderings. We also introduce a mechanism of the charge-6e state via frustration of pair-density-wave state, which may be relevant to the recent hc/6e oscillations observed in the Little-parks type experiments in Kagome superconductors. Furthermore, we also studied the dominant role of Bethe string, i.e., multi-magnon excitations in quantum dynamics when spin chains are close to the field-tuned criticality.

报告人简介：

Congjun Wu received his Ph.D. in physics from Stanford University in 2005, and did his postdoctoral research at the Kavli Institute for Theoretical Physics, University of California, Santa Barbara, from 2005 to 2007. He became an Assistant Professor in the Department of Physics at the University of California, San Diego in 2007, an Associate Professor in 2011, and a Professor in 2017. In 2021, he became a Chair Professor at School of Science, Westlake University. He was selected as a New Cornerstone Investigator in 2023, elected to a Fellow of American Physical Society in 2018, and awarded the Sloan Research fellowship in 2008.

4

报告人：阮善明，Kyoto University

时间：5月30日（周二）14:00

单位：中科院理论物理所

地点：南楼6620

腾讯会议：557-714-677

摘要：

Over the past twenty years, fruitful developments on the interface between quantum information theory, quantum field theory, and quantum gravity are achieved in the framework of the AdS/CFT correspondence. A long-standing and intriguing question is: does the holographic principle apply to cosmologies like de Sitter spacetime? In this work, we consider a half dS spacetime which is closed by a timelike boundary. By employing the holographic entanglement entropy, we argue that gravity on a half dS$_{d+1}$ is dual to a highly non-local field theory without gravity on dS$_d$.

报告人简介：

Shan-Ming Ruan is currently an “It From Qubit” postdoctoral fellow at Yukawa Institute for Theoretical Physics, Kyoto University. He graduated from Lanzhou University and obtained his master's degree under the supervision of Rong-Gen Cai at the Institute of Theoretical Physics, Chinese Academy of Sciences. He obtained his Ph.D. from Perimeter Institute and the University of Waterloo under the supervision of Rob Myers. His research focuses on understanding the interior of black holes via the connections between quantum information and quantum gravity.

5

报告人：衣路英, 新加坡国立大学

时间：5月30日（周二）16:00

单位：北京大学物理学院

地点：物理楼中215会议室

摘要：

近年来，发达国家对高端光电设备的技术封锁越来越严格，使我国光电高科技产业的发展受到了较大影响。探索光学传感的基础科学问题和工程技术难题对强化我国基础前沿研究、推动新型光电传感器和智能设备的产业化都具有极其重要的战略意义和现实意义。报告内容主要是“光学成像传感器与面向医疗健康的光电智能器件的开发与应用”的研究，致力于探索新型光学材料在光学成像传感器制造和可穿戴智能设备中的新机会。

报告人简介：

衣路英，现任新加坡国立大学Research fellow。2020年博士毕业于清华大学精密仪器系，获北京市优秀毕业生；2020年8月至今新加坡国立大学博士后。主要从事新型光电子材料和器件、光学新型成像传感器、基于人工智能的光学可穿戴设备等光学工程和材料交叉融合方向。近年来，以第一（含共同）作者在Nature、Nat. Photonics、Nat. Electron、Nat. Biomed. Eng.等期刊发表论文15篇，研究成果被Nature、Nat. Electron.、Science Bulletin等杂志亮点评述，被BBC、新加坡联合早报和海峡时报等主流媒体报道。

6

报告人：万彪，国科温州研究院

时间：5月31日（周三）15:00

单位：中科院理论物理所

地点：北楼322会议室

摘要：

DNA-binding proteins bind to the target sites by scanning the DNA sequences and locating the specific sequences. The interactions between the protein and specific DNA sequences determine the binding times. Consequently，the protein dissociation rate depends on the specific sequence while the association rate is often assumed to be sequence independent. However, a latest experimental study on sequence-specific recognition and binding of DNA target sites by protein challenges this presumption (Science 375, 442–445 (2022)). The notable anticorrelation between the measured dissociation and association rates seems to suggest that locating targets may be more sensitive to the sequences than departing from targets. To reconcile the conventional presumption and the experimental data, we propose a model that only considers the thermal dynamics of the DNA-protein interactions，which predicts an uncorrelated dissociation and association rates for small proteins and reveals that the anticorrelated distribution between the rates becomes notable only for proteins with large binding-length. This anticorrelated behavior suggests that the rates of locating targets are sufficiently small compared with those of departing from targets, and both of them depend on the non-specific/specific sequences，which gives rise to the anomalous behavior. Our model thus extends the conventional presumption and can help to unravel the experimental data.

报告人简介：

万彪，国科温州研究院副研究员，2017年博士毕业于中国科学院大学，后在北京计算科学研究中心从事博士后工作研究，2022年入职国科温州研究院。主要研究兴趣包括DNA、DNA-蛋白质相互作用及其物理建模等。

7

报告人：叶锦武，Great Bay University，Mississippi State University

时间：5月31日（周三）16:00

单位：北京师范大学物理学系

地点：物理楼106

摘要：

Poincare and Einstein's special relativity says that any physics law in a vacuumtakes identical form in any two inertial frames. On the opposite direction, PW.Anderson'" More is different " says that various macroscopic quantum or topological phenomenaemerge in a material which contains enormous number of interacting particles. In contrastto the relativistic quantum field theory, there is always a reservoir which can exchangeenergy and the particles with a material. It remains an outstanding problem to applyEinstein's special relativity to Anderson's " More is different ". Here we address thisoutstanding problem and find that the combination leads to many new effects. Wedemonstrate these new effects by studying one of the simplest quantum phase transitions(OPT): Superfluid (SF)-Mott transitions of interacting bosons in a square lattice in asample moving with a constant velocity. It is the moving which mixes the space and time.then leads to a emergent space-time near the QPT. It is the existence of reservoir whichmakes crucial differences between a moving sample and a moving inertial frame. We alsostress the important roles played by the underlying lattice. The experimental detection ofthese dramatic new effects in some materials or cold atoms loaded in an optical lattice arediscussed. The lecture is very pedagogical, so should be access to undergraduate studentswith yery basic knowledges on quantum mechanics and statistical mechanics.

报告人简介：

Prof. Ye received his Ph.D. from Yale University. Now he is a Professor at Mississippistate university. Currently, he is a visiting professor at the newly found Great Bayuniversity in Dongguan, Guangdong, China. He is a condensed matter theorist workingon the interdisciplinary field of condensed matter, quantum optics, cold atoms, non-relativistic quantum field theory, Turbulence and conformal field theory. Recently, he hasbeen particularly interested to explore possible deep connections amongquantum/topological phases, Sachdev-Ye-Kitaev models and quantum black holes frommaterial's point of views.

8

报告人：王一男，北京大学物理学院

时间：6月1日（周四）14:00

单位：中科院理论物理所

地点：南楼6620

摘要：

In this talk, I'm going to give a brief survey of the two most important topics in string phenomenology: the swampland conjectures and string landscape. The former one is a set of conjectured constraints on any UV complete quantum gravity theory, while models in the string landscape act as concrete examples that satisfy these conjectures. I will also mention some of my recent works in this field.

报告人简介：

王一男，2013年本科毕业于北京大学物理学院，2018年博士毕业于麻省理工学院物理系，2018-2021年在牛津大学数学系做博士后，2021年至今在北京大学物理学院任助理教授/研究员，博士生导师。王一男的主要研究方向包括弦论、量子场论与数学物理，近年来关注的物理问题包括超对称量子场论、弦唯象学与物理中的广义对称性等。

9

报告人：刘奇航，南方科技大学

时间：6月1日（周四）15:00

单位：北京大学物理学院

地点：物理大楼西楼202报告厅

摘要：

Symmetry formulated by group theory plays an essential role with respect to the laws of nature, from fundamental particles to condensed matter systems. In this talk, we elucidate that the crystallographic symmetries of a vast number of magnetic materials with light elements, in which the neglect of relativistic spin-orbit coupling is an appropriate approximation, are considerably larger than the conventional magnetic groups. Thus, a symmetry description that involves partially-decoupled spin and spatial rotations, dubbed as spin group, is required. We then derive the classifications of spin “point groups” describing coplanar and collinear magnetic structures, and the irreducible co-representations of spin “space groups” illustrating more energy degeneracies that are disallowed by magnetic groups. These new symmetries directly give rise to further discoveries without any relativistic origins, including spin splitting, Z2 topological classification and new quasiparticles. Using angle-resolved photoemission spectroscopy measurements and density functional theory calculations, we demonstrate the existence of such spin splitting effect in a noncoplanar antiferromagnet MnTe2, and the spectral evidence of chiral Dirac fermions in a collinear antiferromagnet CoNb3S6.

报告人简介：

刘奇航，南方科技大学副教授，本科及博士均毕业于北京大学物理学院（2003-2012），曾任美国西北大学博士后、美国科罗拉多大学博尔德分校助理研究员；主要从事计算凝聚态物理研究，研究兴趣聚焦于量子材料中新奇的多自由度耦合现象，包括自旋-局域磁矩-轨道耦合作用下的对称性新理论和新效应，以及相关的新材料设计筛选。发表SCI论文80余篇，H指数34。2018年作为独立PI后发表通讯作者文章30余篇，包括11篇PRL/X、4篇Nat. Commun.、3篇Natl. Sci. Rev.等。2020年作为项目负责人获批国家重点研发计划“量子调控与量子信息”重点专项（青年项目），2022年获批深圳市杰青项目，2021与2022年连续入选斯坦福大学发布的全球前2%顶尖科学家榜单（World’s Top 2% Scientists）。

10

报告人：熊伟志，山东大学

时间：6月1日（周四）14:30

单位：清华大学物理系

地点：理科楼C109

摘要：

质子电荷半径与质子内夸克的空间分布密切相关，而且是量子电动力学对氢原子能级计算所需的重要参数。在2010年，科学家们使用缪子氢原子光谱技术，测量到了当时最精确的半径结果，然而却比之前使用ep弹性散射与常规氢原子光谱技术测量的结果小了7σ，引发了“质子电荷半径之谜” 。近十年来，尽管人们在理论与实验上都取得了一批重要成果，但目前仍有许多问题未被解答，尤其在轻子散射领域。在这个报告中，我将介绍近期的一些散射实验相关的进展，主要将介绍美国杰斐逊实验室的高精度质子电荷半径实验（PRad），以及目前已被批准的新一代PRad-II实验。这个新实验预计会将总误差缩小为PRad实验的四分之一，将成为最精确的散射实验测量结果，对推动高精度实验测量与轻子普适性破坏的搜寻有着重要的意义。

报告人简介：

熊伟志，山东大学前沿交叉科学青岛研究院研究员，齐鲁青年学者，博导。2012年毕业于美国南卡罗莱纳大学，2020年获得美国杜克大学博士学位，于2020-2022年在美国雪城大学做博士后。担任杰斐逊实验室三个实验项目的共同发言人，主要研究方向包括核子结构，尤其是高精度质子电荷半径、核子形状因子、宇称破坏深度非弹性散射的实验测量，以及美国杰斐逊实验室SoLID谱仪与中国未来电子-离子对撞机EicC的软件开发。以主要作者在Nature等杂志发表实验论文十余篇。

11Flatland: Bridging Disciplines, Unveiling the Beauty of Dimensions

报告人：刘政，新加坡南洋理工大学

时间：6月5日（下周一）10:00

单位：中科院物理所

地点：怀柔园区MA楼505会议室

腾讯会议：568-670-509

会议密码：0605

摘要：

In the realm of 2D materials, where disciplines converge, we embark on a captivating journey to uncover the hidden beauty of dimensions. Our exploration begins with the synthesis of transition-metal chalcogenides (TMCs) in the single domain, focusing on 2D magnets based on 3d elements. Expanding our horizons, we delve into the realm of many domains with large-area TMDs. These films boast an astonishingly high density of grain boundaries, influencing their electronic and optical properties and enables grain-boundaries 1D intercalation. Continuing our journey, we present a remarkable breakthrough in 2D amorphous systems — the synthesis of an amorphous single-layer PtSex catalyst. We achieve a remarkably high Pt mass loading, enabling efficient hydrogen generation. This discovery opens up new possibilities for sustainable energy applications. Unveil the boundless beauty that lies within the dimensions of Flatland, where new perspectives, phenomena, and scientific opportunities await.

报告人简介：

Zheng LIU is a professor at Nanyang Technological University, Singapore. He works on the synthesis of high-quality and large-size novel 2D monolayers, especially transition metal dichalcogenides (TMDs) and their applications in catalysis and electronics. He has published > 350 papers with total citations > 50,000 and H-index of > 100. He was the finalist in the World Technology Award in Energy category in 2012. In 2013, he was awarded the prestigious Singapore NRF Fellowship and the elite Nanyang Assistant Professorship. He was awarded ICON-2DMAT Young Scientist Award and the prestigious Singapore Young Scientist Award in 2018. He was named Materials Research Society of Singapore Chair Professorship in 2019 and awarded Asia's Rising Scientists and the Nanyang Research Award (Young Investigator) in the same year. He was the highly cited researcher from 2018 - 2022. Dr Zheng Liu is Editor-in-Chief of Materials Today Catalysis since 2022.

更多报告信息：

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