哈伯德模型、莫尔超晶格、非互易热辐射、三维显示 | 本周物理讲座

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报告 人 ： Rui-Zhen Huang (黄瑞珍)， Ghent university

时间：5月14日（周二）10:00

单位：中国科学院物理研究所

地点：M830

摘要：

Infinite uniform tensor network states are believed to describe gapped quantum phases faithfully. For critical states, a finite entanglement cutoff/scaling has to be applied, which was conjectured to connect a deformed CFT in 1+1d. We extend our previous study to thermal systems, in which the inverse temperature serves as the finite length scale. We argue that as long as the inverse temperature smaller than the finite-entanglement induced scale, the entanglement Hamiltonian in the thermal MPS is also effectively a BCFT with an entanglement and a physical conformal boundary condition. Compared with the finite entanglement scaling, a key difference is that due to the thermal effect, the physical conformal boundary has to respect the full non-anomalous symmetry of the lattice model. In the low-temperature limit, the thermal MPS becomes non-injective and the system enters the finite entanglement scaling regime. We also discuss boundary critical behavior in physical systems with explicit physical boundaries in the thermal MPS framework.

报告人简介：

Rui-Zhen Huang is a BOF Postdoctoral Fellow working with Prof. Frank Verstraete at Ghent university since 2022. He obtained his Ph.D. from the Institute of Physics, Chinese Academy of Sciences in 2018 and continued his research in condensed matter theory as a postdoc at the University of Chinese Academy of Sciences.

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报告人：Dr. Xinyang Dong，Beijing AI for Science Institute

时间：5月15日（周三）10:00

单位：中国科学院物理研究所

地点：M830

摘要：

The mechanism of electronic superconductivity in systems with intertwined orders has been debated for a long time. Several electronic mechanisms have been proposed, but so far there is no unbiased way of attributing superconductivity to any one of them. In this talk, I will present numerical results that quantitatively analyze the nature of superconductivity in a non-perturbative calculation of the two-dimensional Hubbard model within the dynamical cluster approximation. The simulation results show that at intermediate-to-strong interaction strengths, the one-loop spin fluctuation theory can not fully explain the pairing of electrons in the singlet superconducting state. To have a generalized and unbiased way of analyzing all possible fluctuations on equal footing, we generalized the fluctuation diagnostics method to the ordered superconducting state. By analyzing the anomalous self-energy in the superconducting state, our fluctuation diagnostics calculation precisely identifies antiferromagnetic spin fluctuations as the glue of the d−wave pairing.

报告人简介：

Xinyang Dong received her bachelor's degree from Peking University, Yuanpei college in 2017 (physics major). After that, she received her Ph.D. in physics and scientific computing from University of Michigan, Ann Arbor in 2022. Her Ph.D. research focused on the numerical methods for two-particle fluctuations and real-time dynamics of strongly correlated electron systems, especially understanding the mechanism of superconductivity in the Hubbard model from two-particle perspective. She is a researcher at the AI for Science Institute, Beijing currently, working in the interdisciplinary field of machine learning and many-body physics.

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报告 人 ： Guo Yu (于果) , Princeton University

时间：5月15日（周三）14:00

单位：中国科学院物理研究所

地点：M253

摘要：

In solid state materials, numerous electrons are interacting due to Coulomb interactions. In the strongly-correlated regime, interactions can give rise to intriguing quantum phenomena including the appearance of “fractionalized” excitations. Their investigation is critical to fundamental physics and future quantum technologies but is challenging in both material realization and experimental detection. 2D materials and their moiré structures offer a promising platform to search for and investigate such states. In this talk, I will provide a new example of strongly correlated quantum states, i.e. a 2D anisotropic Luttinger Liquid state in small-angle twisted bilayer WTe2. This state exhibits three key transport characteristics, including (i) an exceptionally large in-plane transport anisotropy, (ii) a power-law scaled conductance in the hard direction and (iii) a distinct nonlinear differential resistance along the easy direction that features a vanishing value at zero bias. By tuning the twist angle, we demonstrate that such a 2D correlated state, akin to the 1D Luttinger liquid, can be stabilized down to at least 50 mK. Our results provide a platform for further studying intriguing phenomena related to non-Fermi liquids.

报告人简介：

Guo Yu is a graduate student in Sanfeng Wu group at Princeton University. Her research mainly focuses on detecting novel quantum states of various 2D materials using quantum transport and other techniques. Before Princeton, she obtained bachelor’s degree at Physics Department, Tsinghua University in 2018. She will join Physics Department at Harvard University as a Harvard Quantum Initiative (HQI) postdoc fellow in fall 2024. Her research interest lies in developing next generation quantum devices and experimental probes for correlated 2D quantum states.

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报告 人 ： Prof. Nicolas Regnault， Centre national de la recherche scientifique

时间：5月15日（周三）15:20

单位：中国科学院物理研究所

地点：M234

摘要：

In the realm of condensed matter physics, the fractional quantum Hall effect stands as a singular experimental manifestation of topological order, characterized by the presence of anyons—quasiparticles that bear fractional charge and exhibit exchange statistics diverging from conventional fermions and bosons. This phenomenon, observed over four decades ago, was still missing the direct observation of similar topological orders arising purely from band structure—without the application of strong magnetic fields. In 2023 within the span of a few months, several pioneering experiments have illuminated this once theoretical domain. Studies on twisted homobilayer MoTe2 and pentalayer rhombohedral graphene placed on hBN have finally unveiled the existence of fractional Chern insulators (FCIs), the zero-magnetic field analog of fractional quantum Hall states.

The journey to this point, preceded by over a decade of theoretical frameworks and predictions surrounding FCIs, yet the experimental revelations have proved to be richer and more surprising than expected. In this talk, we will present how the combination of ab-initio and quantum many-body calculations can help us capture the different features observed in experiments. We will discuss the potential future for this exciting booming field, including the possible observation of fractional topological insulators, a yet-never observed topological ordered phase preserving the time reversal symmetry.

报告人简介：

Nicolas Regnault is a CNRS research director at the Ecole Normale Superieure in Paris and a visiting researcher at Princeton University. He did his PhD thesis on integrable models for gravity and then moved to condensed matter. He is a renowned expert in the fractional quantum Hall physics, especially its numerical aspects, topological phases of matter, entanglement properties in many-body quantum states and out-of-equilibrium quantum systems.

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报告 人 ： 刘梦琦， 上海交通大学

时间：5月16日（周四）15:00

单位：中国科学院物理研究所

地点：M253

摘要：

基尔霍夫定律是热辐射领域的基本定律之一，其表明物体的光谱定向发射率与光谱定向吸收率是精确相等的。非互易热辐射指突破传统基尔霍夫定律对称互易限制，使辐射器光谱、角度发射率和吸收率在时间、空间上解耦的辐射传热新方式，非互易能源器件有望突破传统能源器件的能量转化效率极限，在先进热管理、高效能量收集与转换等方面具有重要意义。本报告针对目前非互易热辐射仅能在极窄波段、单一角度下实现且依赖于强外部磁场的问题，提出基于介电常数近零的磁性超材料体系，并提出基于相位奇点的全局非互易吸收/发射调控方法，实现了宽角域、宽频域的非互易热辐射，并进一步拓展了热辐射基尔霍夫定律的内涵，设计了单波段、双波段、超宽谱的非互易热辐射器。

报告人简介：

刘梦琦博士分别于2016年获得山东大学学士学位，2022年上海交通大学博士学位，导师为赵长颖教授，其中2021-2022年于新加坡国立大学Cheng-Wei Qiu教授课题组联合培养，2022年至今在上海交通大学工程热物理研究所开展博士后研究。近年来以第一作者(含共一)在Nature Materials、Nature Photonics、Physical Review Letters等期刊发表论文13篇，授权发明专利5项。入选2022年度博士后创新人才支持计划、上海市超级博士后，主持国家自然科学基金青年项目、中国博士后面上项目等。曾获AUTSE Young Scientist Award, 吴仲华优秀研究生奖，上海市巾帼创新未来之星，上海交通大学优秀博士学位论文等。

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报告 人 ： Kam Tuen Law，The Hong Kong University of Science and Technology

时间：5月15日 （周三）下午3:00

单位：北京大学物理学院

地点：物理楼，西563会议室

摘要：

Recently, it has been observed that superconducting and interaction-driven quantum anomalous Hall states can appear simultaneously in gate-defined Josephson junctions in tiwisted bilayer graphene. The interaction-driven state serves as the weak link in the superconductor/correlated state superconductor Josephson functon. In this talk, we will discuss how the interaction-driven valley polarization is essential for the Josephson diode experiments. Moreover, many of the superconducting properties of moire superconductors with ultra-flat bands deviate greatly from convential BCS theory predictions. In the second half of the talk, I would like to present a Ginzburg-Landau theory derived from a microscopic flat band Hamiltonian, which incorporates the quantum metric effects of moiré flat band superconductors. The theory explains how the length scale defined by quantum metric, which we call the quantum metric length, is critically important in determining the properties of moiré flat band superconductors

报告人简介：

Prof. Kam Tuen Law is a Professor at The Hong Kong University of Science and Technology. He received his BSc degree from HKUST in 2003 and completed his PhD degree at Brown University in 2008. He then worked as a Croucher Postdoctoral Fellow at MIT with Prof. Patrick Lee. He joined HKUST as an assistant Professor in 2011. Prof. Law did pioneer works on the study of Majorana fermions in topological superconductors, including predicting the quantized tunnelling conductance and spin-selective Andreev reflections induced by Majorana fermions. He co-discovered Ising superconductivity in transition metal dichalcogenides with two experimental groups in 2015 and has since uncovered many novel properties of Ising superconductors theoretically. Recently, he predicted new classes of materials called Kramers nodal line metals and spin-orbit-parity-coupled superconductors. Many of his theoretical predictions were verified experimentally. Prof. Law received the Croucher Innovation Award in 2015 and the Achievement in Asia Award by the International Organization of Chinese Physicists and Astronomers in 2024. He is a Hong Kong Research Grants Council Research Fellow (2020) and the Founding President (2018-2021) of the Hong Kong Young Academy of Sciences.

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报告 人 ： 陈国瑞，上海交通大学

时间：5月16日（周四） 15:00

单位：北京大学物理学院

地点：物理楼，西563会议室

摘要：

二维材料层间的多种堆垛方式，为调控二维材料的物性提供了一个新的维度。在这个报告中，我将介绍一种简单的堆垛控制，即天然石墨晶体中广泛存在的一种特殊层间堆垛形式，菱方堆垛（ABC堆垛）。我们开发了一套制备高质量ABC堆垛石墨烯器件的方法，成功在ABC堆垛的三层石墨烯和四层石墨烯中观测到了一系列强关联和拓扑电子物态。具体的，我们在ABC三层石墨烯和氮化硼组成的莫尔超晶格中，观测到了莫特绝缘体、超导和陈绝缘体；在ABC四层石墨烯单晶中，我们发现了层间反铁磁绝缘体和准自旋极化的金属态；通过引入自旋-轨道耦合，我们在四层石墨烯电中性点上发现了高陈数的量子反常霍尔效应。

报告人简介：

陈国瑞，本科毕业于山东大学，博士毕业于复旦大学，随后在加州大学伯克利分校从事博士后研究，2020年底加入上海交通大学物理与天文学院，任长聘教轨副教授、独立PI。从事凝聚态物理实验研究，主要关注石墨烯等二维材料及其异质结中出现的新奇物态和电输运的研究。

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报告 人 ： 朱华星，北京大学

时间：5月15日（周三）9:30

单位：中国科学院理论物理研究所

地点：南楼6520

摘要：

Correlation functions of local operators are ubiquitous objects in quantum field theory. Four-point correlation functions in supersymmetric or conformal field theories have been an active area of research in th past decades. However, it is somewhat surprising that four-point correlators in Quantum Chromodynamics (QCD) are barely understood, despite their important relation to physical scattering cross sections. In this talk, I will briefly review previous understanding of supersymmetric four-point correlators in the null polygon limit, where consecutive points are near their light cone. Then, I will introduce a new approach to address the problem using Soft-Collinear Effective Theory, which allows generalization to QCD.

报告人简介：

朱华星教授2007年本科毕业于北京大学，2012年在北京大学获得博士学位。2012年至2017年分别在斯坦福直线加速器中心和MIT从事博士后研究。2017年至2023年6月任浙江大学百人计划研究员，2023年7月起任北京大学物理学院长聘副教授。朱华星的主要研究方向是量子场论，微扰量子色动力学和软共线有效理论。他入选2017年国家海外高层次青年人才，是2020年香港求是基金会求是青年学者和2023年首届亚洲青年科学家基金物质科学研究员。

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报告 人 ： Hiroyuki Sagawa，University of Aizu

时间：5月16日（周四）14:00

单位：中国科学院理论物理研究所

地点：北楼322

摘要：

The self-consistent Hartree-Fock (HF)+subtracted second random phase approximation (SSRPA) calculations based on the Skyrme energy density functions (EDFs) are performed for the Gamow-Teller (GT) excitations of four closed shell nuclei 48Ca, 90Zr, 132Sn, and 208Pb to study the systematic trend of SSRPA on the description of GT strength distributions with respect to the excitation energy and the width. We apply also the SSRPA model including tensor force to the decay half-lives in magic and semi-magic nuclei, 34Si, 68, 78Ni and 132Sn with Skyrme EDFs. The inclusion of the two particle-two hole (2p-2h) configurations in the SSRPA model shifts low-lying GT states downwards. It leads to an increase of the β decay phase space, which ensures the half-lives of the four nuclei are finite and reduces the β decay half-lives dramatically. The effect of tensor interaction on the β decay half-life in SSRPA model is also pointed out to change largely the half-lives by about one to two orders of magnitude with respect to the ones obtained without tensor force. We further study magnetic dipole (M1) transitions of magic nuclei to disentangle the role of triplet-even and triplet-odd tensor forces in the spin-isospin excitations.

报告人简介：

Prof. Hiroyuki Sagawa is a theoretical physicist specializing in collective motion in nuclei, spin-isospin excitations, exotic nuclei, charge symmetry breaking in nuclei and hypernuclei. He obtained his Ph.D. in Physics from Tohoku University in 1975, focusing on nuclear theory. He has worked at the University of Tokyo, Utsunomiya University, Niels Bohr Institute, Universié de Paris-Sud, National Institute of Nuclear and High Energy Institute (NIKHEF) at Amsterdam, Michigan State University, and the University of Aizu. Now, he is a Senior Visiting Scientist at RIKEN Nishina Center and a Professor Emeritus at the University of Aizu.

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报告 人 ： 刘娟，北京理工大学

时间：5月16日（周四） 10:00

单位：福建师范大学，光学与信息工程学院，信息光子学研究中心

链接：

摘要：

几个世纪以来，真三维显示一直是人们所追求的终极显示目标。传统的双目视差型三维显示技术存在辐辏调节冲突，长时间观看会导致人眼视疲劳问题。因此发展符合人眼生理认知习惯的高分辨率动态三维显示技术成为当下的研究热点，目前主流的解决方案包括基于光场三维显示和全息三维显示技术。本次报告将从这两个方面开始，结合北京理工大学在该领域的研究成果，简介真三维显示技术的发展历程，重点讲述最新的研究动态，并针对当前存在的问题，探索可行的解决方案。最后，对真三维显示技术的未来进行展望。

报告人简介：

刘娟，北京理工大学教授，博导。长期从事三维显示、全息和衍射光学领域的教学和科研工作。承担国家自然基金重点/国际合作重点/区域联合重点/面上项目、科技部973/863课题、国家重点研发课题、北京市科委项目及企业联合开发项目等20余项。兼任中国光学学会全息与光学信息处理专委会副主任委员、国际信息显示学会（SID）委员、SID 中国区域AR/VR 专题主席、《光学技术》的执行主编、国际期刊Optik编委等。曾任国际期刊Applied Optics编委和特刊责任主编、国际数字全息会议DH（2019～2020）大会主席、国际会议OIT-1（2019～2024）主席。在国际光学期刊Nature Communications、Light、Optics Letters等发表论文200 余篇，部分成果被Springer Nature 选为ESI 热点及高被引论文，申请发明专利70余项，授权50余项。

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