超表面、自旋波、石墨烯凱庫勒超晶格、 kagome金屬 | 本周物理講座

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報告人：柴國志，蘭州大學

時間：3月24日（周二）10:00

單位：中國科學院物理研究所

地點：懷柔園區X1南樓101會議室

騰訊會議：300-570-941

摘要:

自旋波(磁振子)作為自旋角動量傳遞的基本表現形式反映了自旋的眾多本征物理特性而引起廣泛關注。磁振子由其運動方程決定具有天然的手征性。我們最近工作表明：利用層間相互作用和邊界調制可實現表面自旋波的色散非互易行為，并基于此可得到自旋波的負群速度現象。在單層磁性薄膜中可實現靜磁表面波和垂直交換駐波磁振子之間的耦合現象，并得到在相反波矢下耦合的非互易現象。在多層膜中則可以利用層間耦合實現聲學支磁振子和光學支磁振子間的超強耦合。在最后也將分享一些本課題組在磁性雙層膜中發現的一些新的磁振子耦合現象。

報告人簡介:

柴國志，蘭州大學“萃英學者”，二級教授，博士生導師。入選國家級青年人才計劃，是甘肅省杰出青年基金獲得者、甘肅省領軍人才。2006年、2012年分獲蘭州大學學士和博士學位。2011年留校，在物理科學與技術學院工作至今，歷任講師，副教授和教授。近年來主持國家自然科學基金5項，其他各類項目7項。在高頻磁性材料與磁功能器件研究方面發表SCI論文90余篇，獲授權發明專利4項。目前主要從事高頻磁性材料及其在傳感器中的應用、磁性功能器件、布里淵光散射、微波光子-磁振子耦合等方面的研究。

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報告人：張翼，南京大學物理學院

時間：3月24日（周二）13:30

單位：中國科學院物理研究所

地點：M樓249會議室

摘要:

借助各種表界面超晶格的構造來實現新穎量子物態的構筑是近年來凝聚態物理研究中的熱點問題。以石墨烯為代表，通過構造具有(√3×√3)R30°超晶格周期的凱庫勒畸變（Kekulé-distortion）可以實現狄拉克錐向布里淵區中心折疊并打開能隙。本報告將介紹多種表界面元素摻雜方式實現石墨烯凱庫勒超晶格的構筑與狄拉克電子調控。我們利用角分辨光電子能譜技術，發現石墨烯表面的無序雜質可誘導增強狄拉克電子的谷間彈性散射，在轉變溫度以下，散射狄拉克電子間的相互干涉可形成凱庫勒超晶格有序態，進而將布里淵K/K’點的兩套不等價的狄拉克錐折疊到布里淵區中心。對于具有重電子摻雜效應的表面吸附鉀元素，則會產生明顯的等離激元并使狄拉克能帶重整化，進而抑制狄拉克錐的折疊效應。釓元素在外延石墨烯的界面插層可增強其表面吸附能力，在低溫下通過吸附氮元素來形成凱庫勒周期并產生能帶折疊。銪（Eu）元素在外延石墨烯的界面有序插層可直接形成凱庫勒超晶格，更為重要的是，我們發現石墨烯狄拉克電子在能帶折疊過程中，會插層銪元素4f軌道電子的局域磁矩產生很強的交換耦合作用，由此使得折疊狄拉克能帶產生巨大的劈裂行]。這種狄拉克電子與局域磁矩之間的交換耦合作用，為狄拉克費米子的調控提供了新的自由度；而所實現的折疊狄拉克能帶的巨幅劈裂，對于推動凱庫勒石墨烯在自旋電子學領域的實際應用、探索基于狄拉克電子關聯作用下的新穎量子物態，均具有重要的科學意義。

報告人簡介:

張翼，南京大學物理學院教授。2006年畢業于北京大學。2011于中國科學院物理研究所取得博士學位。2011-2015年在美國伯克利國家實驗室和美國斯坦福大學從事博士后研究。2015年加入南京大學物理學院。主要從事新型二維量子材料的分子束外延生長及新穎低維量子物態的構筑與調控研究，迄今已發表學術論文60余篇，H因子30。主持國家重點研發計劃、基金委重大研究計劃重點支持項目等多個國家項目。2021-2025年入選愛思唯爾中國高被引學者。2023年入選科睿唯安“全球高被引科學家”。

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報告人：朱彬，南開大學

時間：3月26日（周四）10:00

單位：中國科學院理論物理研究所

地點：南樓6620

摘要:

With the new notions of flat holography introduced in recent years, there has been increased interest in relating the new formalisms to the flat space limit of AdS/CFT. We study Carrollian amplitudes of massless scalars in (1+2) Minkowski space. Using the prescription recently shown by Alday et al. originally designed for the AdS4 Witten diagrams, we show that AdS3 Witten diagrams in position space in the flat space limit reduce to Carrollian amplitudes. The flat space limit in the bulk is implemented by the Carrollian limit at the boundary. Focusing on four-point correlators with contact and exchange diagrams, we show that the Carrollian limit makes the universality of the bulk point singularity manifest upon performing analytic continuation to the Lorentzian signature of the boundary correlators. Unlike four-point Carrollian amplitudes in (1+3) dimensions, the (1+2) dimensional ones are non-distributional, having analytic properties simpler than the AdS correlators. We also report the first observation of a double copy structure of Carrollian amplitudes.

Generalizing the result to higher spacetime dimensions, we use the scattering equations and ambitwistor strings to prove the correspondence between an appropriate flat limit of boundary correlators in AdS and Carrollian scattering amplitudes – massless amplitudes written in position space on the null conformal boundary – for any number of external states and spacetime dimensions in tree-level, cubic scalar theories. We first derive the Carrollian version of the scattering equations in Minkowski space and their associated Carrollian amplitude formulae, by direct Fourier transform from momentum space and from ambitwistor strings with a Carrollian basis of vertex operators. We then take the flat limit of known formulae for all tree-level boundary correlators of cubic scalar theories in AdS, recovering the Carrollian amplitudes in flat space. In the special case of AdS3, we also make some comments on the flat space limit of spinning boundary correlators.

報告人簡介:

朱彬，南開大學物理科學學院副教授。2022年博士畢業于美國東北大學，導師為Tomasz Taylor。2022年至2025年先后在加拿大圓周理論物理研究所和英國愛丁堡大學做博士后。于25年底加入南開大學物理科學學院，研究方向為散射振幅、共形場論和平直時空的全息理論，在PRL, JHEP, PRD, PLB, NPB等期刊發表19篇SCI論文。

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報告人：何頌，Intitute of Theoretical Physics, Chinese Academy of Sciences

時間：3月26日（周四）15:00

單位：中國科學院理論物理研究所

Zoom：894 8844 8450

Passcode：441769

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報告人：柳仲楷，上海科技大學

時間：3月26日（周四）15:00

單位：北京大學物理學院

地點：物理大樓中212報告廳

摘要:

Magnetic kagome materials provide a unique platform for exploring magneto-transport phenomena, symmetry breaking, and charge ordering driven by the intricate interplay among electronic structure, topology, and magnetism. Herein, we introduce a new design strategy for interweaving quasi-1D magnetic Tb zigzag chains with nonmagnetic Ti-based kagome bilayers in TbTi3Bi4. Neutron diffraction, spin-polarized scanning tunneling spectroscopy, and angle-resolved photoemission spectroscopy analyses confirm that the interwoven structure exhibits a coexistent elliptical spiral magnetic order, a spin-density wave, and an unusually large band-folding gap. The combined unique magnetic and electronic state leads to a giant anomalous Hall conductivity of 10? Ω?1cm?1. These results establish TbTi3Bi4 as a model system of magnetic kagome metals with strong electron–magnetic interactions.

報告人簡介:

柳仲楷，上海科技大學長聘副教授，研究員，萬人計劃領軍人才，2006年于清華大學獲理學學士學位；2014年于美國斯坦福大學獲得物理學博士學位；2015年7月加入上海科技大學物質科學與技術學院。研究方向為開發并利用角分辨光電子能譜技術研究先進材料電子結構，在拓撲量子材料、低維量子材料、磁性量子材料等方面取得代表性成果。包括拓撲半金屬、磁性拓撲絕緣體、拓撲超導材料、磁性Kagome材料等。主持開發上海同步輻射光源BL07U NanoARPES線站。主持基金委重點項目、科技部重點研發計劃等多項項目，發表包括Science, Nature及其子刊，PRL等在內期刊論文百余篇，引用超23000次。

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報告人：Jianglai Liu，上海交通大學

時間：3月26日（周四）15:30

單位：北京大學物理學院
地點：KIAA-auditorium

摘要:

Dark matter and neutrinos are among the most elusive neutral particles that permeate our Universe. The PandaX (Particle and Astrophysical Xenon) experiment, located in the China Jinping Underground Laboratory beneath a 2400-meter rock overburden, has been at the forefront of the search for dark matter particles for nearly two decades. As the sensitivity of the experiment continues to improve, the experiment has evolved into a versatile particle astrophysics observatory, with particular potentials on neutrino physics. In this talk, I will present the latest development in this field, and project the prospects of PandaX in the decades to come.

報告人簡介:

Jianglai Liu obtained his B. S. degree in Physics from Nanjing University in 1998. He received a Ph.D. degree in Physics in 2006 from the University of Maryland at College Park. He held a postdoctoral and then senior postdoctoral scholar position at Caltech from 2006 to 2010. He joined the School of Physics and Astronomy (SPA), Shanghai Jiao Tong University in 2011, and became a full professor in 2016. He serves as the Deputy Director of the Tsung-Dao Lee Institute (TDLI), and is a Hongwen Distinguished Professor jointly appointed between TDLI and SPA. He has worked on various experiments in the intersections of nuclear physics, particle physics, and astrophysics. He currently serves as the spokesperson of the PandaX experiment, a xenon-based dark matter and neutrino experiment at the China Jinping Underground Laboratory. He also has a strong involvement in the Daya Bay and JUNO experiments, studying the fundamental properties of neutrinos. He was awarded the Outstanding Junior Investigator from the National Natural Science Foundation of China in 2015. He received the Wang Ganchang Prize from the Chinese Physics Society and the Xplorer Prize from the Tencent Foundation (2019). Since 2023, he has been sponsored as a New Cornerstone Investigator (www.newcornerstone.org.cn).

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報告人：Alexander Belavin，L. D. Landau Institute for Theoretical Physics, Russian Academy of Sciences

時間：3月26日（周四）16:00

單位：中國科學院理論物理研究所

Zoom: 894 8844 8450

Passcode: 441769

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報告人：Cheng-Wei Qiu, National University of Singapore

時間：3月26日（周四）16:00

單位：清華大學物理系

地點：物理樓W101

摘要:

In this talk, I will introduce a few new thoughts and developments on metasurfaces and metaphotonics, especially when multiple symmetries of low-dimensional materials meet with man-made structures. Translational research and metasurface spin-offs from our lab will be discussed too. Metasurfaces and low-dimensional materials have been developing as important candidates in the interfacial engineering, providing a plethora of new possibilities in novel optoelectronic functions and applications. The synergies between those domains hold great promises in manipulating light-matter interaction. I will start from reviewing and reporting some of the most recent developments in metasurfaces and nanophotonics, and then focus on how monolayer TMDC and layered 2D materials could be hybridized with classic metasurfaces to modulate and structure novel light behavior, such as zero-dark-current and bipolar semimetal photodetector, monolayer meta-lens of atomic thickness, hybrid designs with enhanced SHG, PL, and tunable structural colors, by the coordinated hybridization between those two parties. Finally, we will elaborate our new breakthrough based on the fusion and integration of symmetry and topological physics with van der Waals polaritonic metasurfaces, as a new roadmap toward ultra-low loss, long-range propagation, topological interfaces, and tailorable on-chip integrated functional devices.

報告人簡介:

Cheng-Wei Qiu is Provost’s Chair Professor in National University of Singapore. He is the recipient of President’s Science Award 2023, the highest science distinction in Singapore. He was elected Fellow of Academy of Engineering Singapore, and Fellow of ASEAN Academy of Engineering and Technology. He is Fellow of APS, Optica, SPIE and The Electromagnetics Academy, US. He is Foreign Fellow of Chinese Optical Society. He is well known for his research in structured light and interfaces. He has published over 600 peer-reviewed journal papers, with H-index of 141. He was the recipient of MIT TR35@Singapore Award in 2012, Young Scientist Award by Singapore National Academy of Science in 2013, Engineering Researcher Award 2021 in NUS, World Scientific Medal 2021 by Institute of Physics, Singapore, Achievement in Asia Award (Robert T. Poe Prize) by International Organization of Chinese Physicists and Astronomers in 2022, Miller Visiting Professorship in UC Berkeley in 2025, Joseph Fraunhofer Award 2026 by Optica, etc. He was Highly Cited Researchers since 2019 by Web of Science. As an overseas partner, he has been awarded China’s Top 10 Optical Breakthroughs for 6 times (2019, 2020, 2021(one in Fundamental Research, and one in Applied Research), 2023 , 2025). He has been serving in Associate Editor for various journals such as JOSA B, PhotoniX, Photonics Research, and Editor-in-Chief for eLight. He also serves in Editorial Advisory Board for Laser and Photonics Review, Advanced Optical Materials, and ACS Photonics.

封面圖片來源：https://www.kunming.cn/news/c/2024-08-28/13869052.shtml

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