kagome超导体 CsV3Sb5、交错磁体、光电半导体表界面调控分子 | 本周物理讲座

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报告人：徐健，北京理工大学

时间：7月22日（周二）9:30

单位：北京大学物理学院

地点：物理中楼215

摘要：

服务碳中和战略需求，光电材料的设计面临多维度、多尺度与多目标的复杂挑战。本报告将介绍我们在光电材料设计中，融合理论计算、机器学习与大模型技术，开发新型表界面分子与新型半导体材料的研究成果，重点包括：（1）开发自动化多维筛选方法，以数据驱动构建静态分子特征与精准缺陷钝化关系的模型，设计新型表界面分子实现载流子高效产生和输运；（2）利用时间尺度吸附动力学，揭示杂化半导体在多种老化环境下的缺陷动态演化机制，基于此提出具有针对性的分子结构优化策略，为抑制表界面降解提供全新的理论思路；（3）提出“双性掺杂”和“翻转带边”的能带结构设计新方法，指引实验合成多种无铅层状双钙钛矿新材料；（4）初步搭建钙钛矿光电领域的垂类大语言模型PerovXpert，在文献语义抽取等多个任务中展现出优于通用大模型的表现，有助推动钙钛矿材料研究的信息智能化进程。

报告人简介：

徐健，女，北京理工大学准聘教授，博士生导师，国家级青年人才。2020年毕业于清华大学，获工学博士学位，2021-2024年在加拿大多伦多大学电子与计算机工程系开展博士后研究工作，2024年6月入职北京理工大学前沿交叉科学院。现主持国家自然科学基金优秀青年科学基金项目（海外）、北京理工大学特立青年学者项目。曾获中国科学十大进展、清华大学优秀博士学位论文、清华大学材料学院研究生学术新秀、清华大学优秀博士毕业生等荣誉。研究方向为半导体光电材料的计算与设计，利用理论计算、数据驱动和人工智能方法，设计新型表界面分子和新型半导体材料，指引实现高效率高稳定性的光电器件（太阳能电池、LED显示器件等）的可控制备。迄今以第一作者/通讯作者（含共同）发表SCI论文30余篇，包括Nature (3篇)，Science (4篇)，Nature Materials，Nature Energy (2 篇)，Nature Photonics，Nature Communications (2篇)，Journal of the American Chemical Society (2篇)，Advanced Functional Materials (4篇)等。担任Nature、Nature Energy, Nature Communications、Journal of the American Chemical Society等多个期刊审稿人。

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报告人：Philippe Bourges，Laboratoire Léon Brillouin, CEA Saclay, 91191 Gif sur Yvette, France

时间：7月22日（周二）10:00

单位：中国科学院物理研究所

地点：M236会议室

摘要：

In many quantum materials, strong electron correlations lead to the emergence of new states of matter. In particular, the study in the last decades of the complex phase diagram of high temperature superconducting cuprates highlighted intra-unit-cell electronic instabilities appearing at the pseudogap temperature. The observed intra-unit-cell order is breaking discrete Ising-like symmetries, while preserving the lattice translation invariance. It is currently interpreted as the magnetic hallmark of loop current order, breaking both parity and time-reversal symmetries. We perform polarized neutron diffraction experiments in underdoped and detwinned YBa2Cu3O6.6 sample, that indicate a hidden local magnetic quadrupling (2x2) of the unit cell at short range. Together with the intra-unit-cell order, these new results suggest a real space hidden magnetic texture of the CuO2 unit cells hosting loop currents.

报告人简介：

Philippe Bourges is a distinguished scientist (PhD in 1989 at University of Rennes and habilitation in 2003 at University of Orsay in France). He is the group leader of superconductivity and neutron scattering at Laboratoire Léon Brillouin at CEA Saclay.He has a long track record about neutron scattering studies in condensed matter with more than 200 publications and 10000 citations with numerous works on high temperature copper-oxide superconductors. He discovered a novel magnetic order in 2006 establishing the concept of loop current. This work was awarded in 2020 by the “Science and Innovation” prize of the French Academy of Sciences. In parallel, he has been involved in the development of neutron spectroscopy instrumentation, in particular the use of polarized neutron diffraction, and the building of the future spectroscopy instrument BIFROST at the European Spallation Source (ESS) in Lund (Sweden).

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报告人：William Liege，Laboratoire Léon Brillouin,CEA Saclay,91191 Gif sur Yvette,France

时间：7月22日（周二）10:30

单位：中国科学院物理研究所

地点：M236会议室

摘要：

The kagome metal, CsV3Sb5, exhibits both a charge density wave phase below 94K with a 2x2 doubling of the unit cell and a superconducting phase below 2.5K. These materials also show strong anomalous Hall effect, but no spin ordering has been found in these materials both by muon spin spectroscopy and neutron diffraction. To explain this without relying on spins, the possibility of an orbital magnetism coming from a loop current phase, emerging alongside the charge density wave, has been theoretically predicted. This phase exhibits some similarities with the current loop phase predicted and observed in cuprates. To check for the presence of this loop current phase in kagome materials, we carried out polarized neutron diffraction experiments on the IN22 (CRG-CEA) triple-axis spectrometer located at ILL-Grenoble. This measurement was experimentally challenging and went close to the limit in accuracy obtainable with polarised neutron diffraction in a reasonable time. Most models predict loop currents to produce magnetic intensity at M1 = [1/2 0 L] or M2 = [1/2 1/2 L] reciprocal space positions with L = {0,1/2}. We investigated both momentum positions. For the first one, no magnetic signal was observed ruling out the possibility of having a magnetic moment larger than 0.01 μB by vanadium atoms. However, measurements at M2 do not exclude the possibility of a magnetic signal, suggesting a moment of only 0.02 ± 0.01 μB per unit cell. This shows that current models have to be refined whether toward a lowering of the expected magnetic moment or toward a different loop current pattern giving rise to magnetic intensity at different reciprocal space positions to be compatible with our measurements.

报告人简介：

William Liege made his master graduation in 2023 at the Grenoble University. He is doing now a PhD at Laboratoire Leon Brillouin with Philippe Bourges about loop currents in cuprates and kagome superconductors. His talk will be about the kagome superconductor, CsV3Sb5·

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报告人：宋成，清华大学材料学院

时间：7月22日（周二）19:30

单位：Frontiers of Physics编辑部、蔻享学术

链接：

摘要：

交错磁体作为第三类磁有序新材料，在结合了反铁磁高本征频率、无杂散场、抗磁场干扰等优势的基础上，又融合了铁磁材料能带劈裂带来的显著的探测信号，其发现入选《科学》期刊评选的2024年度十大科学突破。此报告将首先介绍交错磁体概念并综述其主要实验进展，然后聚焦三类典型的交错磁体RuO2、Mn5Si3和CrSb。在RuO2薄膜中发现了交错自旋劈裂力矩效应及三阶霍尔效应，并通过电学方法实现了对交错自旋劈裂效应的高效调控；观察到自旋相关塞贝克效应与帕尔贴效应，上述效应源于交错磁体的自旋劈裂能带，并利用后者实现了RuO2磁畴成像，证实了交错磁体中存在分区择优的0度或180度磁畴。在Mn5Si3薄膜中观测到电学驱动的奈尔矢量180度翻转，获得了与交错自旋劈裂能带直接相关的磁非线性霍尔效应。在晶体对称性维度实现了CrSb交错磁性的高效调控，揭示了交错磁体的晶格指纹特征，提出了交错磁体全电学翻转的物理判据，为突破高性能交错磁体磁随机存储器的数据读写技术奠定了基础。

报告人简介：

宋成，清华大学材料学院长聘教授，为先书院副院长，先进材料教育部重点实验室主任。2004年和2009年分别在中南大学和清华大学获得学士和博士学位，2009-2011年在德国雷根斯堡大学做洪堡学者，随后开始在清华大学任教至今。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声耦合器件。出版《自旋电子学材料与器件》专著一部，在Nature和Nature Materials等期刊发表学术论文300余篇，引用17000余次。2022年获批国家杰出青年科学基金。曾获2012年度国家自然科学二等奖（第3完成人）、2025年度教育部自然科学一等奖（第1完成人，已公示）和全国“首届卓越青年研究生导师”奖励基金。兼任中国材料研究学会常务理事/青委会主任和中国真空学会理事/薄膜专委会主任。

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报告人：Mirjam Cvetič，University of Pennsylvania

时间：7月23日（周三）15:00

单位：中国科学院理论物理研究所

地点：南楼6620

Zoom Meeting ID: 831 5569 4911

Passcode: 965485

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报告人：Mao Zeng，Research Fellow，University of Edinburgh

时间：7月23日（周三）15:00

单位：南方科技大学物理系

链接：

摘要：

The detection of gravitational waves by LIGO/VIRGO in 2015 opened up a new era of multi-messenger astronomy. Precise theoretical predictions for gravitational wave signals require a combination of numerical simulations and analytic perturbative calculations. Surprisingly, quantum field theory has emerged as a powerful new framework for understanding classical systems, specifically the post-Minkowskian expansion in general relativity. We combine a wide range of tools in theoretical high-energy physics, including on-shell methods for scattering amplitudes, the double copy, effective field theory, and advanced techniques for Feynman integrals. We obtain many new results beyond the reach of direct classical methods, such as the conservative dynamics of spinless binary systems at the 4th post-Minkowskian order, as well as the discovery of new hidden symmetries in spinning binary systems.

报告人简介：

Mao Zeng is a Royal Society University Research Fellow at the Higgs Centre for Theoretical Physics, University of Edinburgh. He obtained bachelor and master degrees from Cambridge University, U.K., and PhD from Stony Brook University, USA, under the advisor Prof. George Sterman. His research uses quantum field theory to make precise predictions for fundamental physics experiments, including colliders and gravitational wave detectors. His research brings together a wide array of theoretical developments in high energy physics, including modern methods for scattering amplitudes, state-of-the-art techniques for Feynman integrals, and effective field theories. He received the Frontiers of Science Award in the first International Congress of Basic Science in Beijing in 2023.

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报告人：王华嘉，中国科学院大学/KITS

时间：7月25日（周五）9:00

单位：中国科学院理论物理研究所

地点：北楼322

摘要：

When a local QFT is coupled to gravity, properties of its energy (or more generally the stress tensor) density expectation values play a crucial role in the gravitational dynamics. Classical conjectures of the stress tensor density (known as the energy conditions) are easily violated in QFTs. Conjectures about the quantum versions of the energy conditions (e.g. ANEC, QNEC) were proposed. Much progresses have been made in the recent decade for understanding and proving these quantum energy conditions. Their origins were found surprisingly in the universal properties of the entanglement structures of the QFTs. In this lecture series, I will review the developments related to the quantum energy conditions, emphasizing on the recent progresses of entanglement-based proofs.

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报告人：林一瀚，北京大学

时间：7月25日（周五）10:00

单位：中国科学院理论物理研究所

地点：南楼6520

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