量子自旋液体、量子模拟、低维纳米有源器件、复杂系统的涌现、暗物质、量子计算机 | 本周直播物理讲座

报告人：林熙，北京大学

时间：8月20日（周四）15:00-16:00

单位：中科院物理所

参加方式：讲座以线上形式进行，采用“腾讯会议”软件

会议ID：841 951 398

会议密码：0820

直播链接： 

https://meeting.tencent.com/l/3tumZ7pVkWmG

摘要：

本报告将介绍目前量子计算和量子模拟中的实验方案和所需要的低温条件，以及不同实验方案中的低温环境的实现手段、特点和搭建的难易程度，并讨论服务于量子计算和量子模拟的低温实验条件可能的发展趋势和面临的挑战。

报告人简介：

林熙，本科毕业于中国科学技术大学，博士毕业于宾州州立大学，现为北京大学量子材料科学中心副教授，主要工作经历为极低温条件下的物性测量和实验技术研发，工作关注重点现为介观条件下的量子输运。

报告人：Dr. Qisi Wang, University of Zurich, Switzerland

时间：8月18日（周二）16:00

单位：中科院物理所

参加方式：讲座以线上形式进行，采用“腾讯会议”软件

会议ID：967 761 089  

会议密码：0818

直播链接： 

https://meeting.tencent.com/l/8FDd22gBowZA

摘要：

High transition temperature (Tc) superconductivity in cuprate materials has been a subject of intense interest in condensed matter physics. Competing interactions in these materials lead to a rich phase diagram with intertwined spin, charge/orbital and lattice degrees of freedom. Unveiling the physical principles of such phases is critical for establishing the defining parameters of superconductivity. Resonant inelastic x-ray scattering (RIXS) is a powerful probe of multiple electronic correlations. With the tremendous improvement of energy resolution, RIXS has now revolutionized the study of elementary excitations in high-Tc materials. In this talk, I will present our recent progress using high-resolution RIXS to explore the interactions behind cuprate high-Tc superconductivity, including the works on (1) understanding the charge ordering in La-based cuprates from a unifying picture, and (2) revealing the origin of phonon anomaly in stripe-ordered cuprates.

报告人简介：

Dr. Qisi Wang obtained his PhD in condensed matter physics at Fudan University in 2018 under the supervision of Prof. Jun Zhao. Since then, he has been working as a postdoc researcher with Prof. Johan Chang at University of Zurich. He uses multiple scattering techniques including neutron scattering, resonant inelastic x-ray scattering and x-ray diffraction to investigate the quantum phases in correlated electron systems such as unconventional superconductors and frustrated magnets.

报告人：孙皓，清华大学

时间：8月19日（周三）19:30

单位：《半导体学报》

参会方式：蔻享直播

直播链接：https://www.koushare.com/lives/room/837107

摘要：

微纳光电子技术不仅是战略性技术，同时是多学科交叉的前沿性研究领域。具有超低功耗、超快响应、超高集成度等特点的纳米尺度光放大器和激光器是硅基片上光子集成及光互连芯片的核心器件和关键技术，对未来超算和片上数据中心等信息技术至关重要，因而成为近年来学术界和产业界共同关注的焦点之一。

报告人简介：

孙皓，清华大学电子工程系副研究员。物理电子学博士，期间赴美国加州大学伯克利分校留学。研究兴趣包括低维半导体材料（纳米粒子/纳米线/二维材料）的发光物理及片上集成有源器件等方面的研究，致力于利用新工艺及先进测试手段探索纳米结构的新效应、新机制和新功能。

报告人：郑志刚，华侨大学

时间：8月18日（周二）14:30

单位：Frontiers of Physics编辑部，高教社自然科技期刊中心

参会方式：蔻享直播

直播链接：https://www.koushare.com/lives/room/584192

摘要：

21世纪是复杂性研究的世纪。凡是包含大量单元、表现出各种集体行为的系统都是复杂系统。典型的例子包括物理化学中的复杂流体、软物质、生物体及其组成生物体的各级结构、生物群体、社会系统、经济系统、电力系统等。复杂系统会在不同层次上产生各种各样的集体涌现行为，表现出一些典型的时间与空间结构及动力学。在诸多涌现行为中，时间的整体非平衡动态行为在很多情况下是非平庸且可分析的，其中最简单的动态就是周期振荡，而最简单的协同行为就是同步。复杂系统集体振荡与同步等行为的出现意味着有序的涌现。复杂系统涌现动力学问题的讨论需要用系统科学的研究范式来加以开展，例如用统计物理学的方法来分析系统宏观量的变化，用网络的思想来探索复杂性的拓扑特性，利用非线性动力学理论来分析序参量的动力学转变与分岔。在本次报告中，我将集中于与复杂系统涌现行为有关的课题近年来的进展，并就几个典型问题来讨论复杂系统集体行为的可分析性与可操作性，就复杂系统涌现动力学研究的一般范式进行探讨，对未来探索给出展望。

报告人简介：

郑志刚，华侨大学二级教授，荟萃计划、闽江学者特聘教授、福建省百人计划、高层次领军人才，系统科学研究所所长，非平衡与复杂系统创新团队学术带头人，博士生导师。第三届全国百篇优秀博士学位论文奖、教育部高校青年教师奖、教育部首批优秀骨干教师等获得者。曾任美国加州理工学院高级访问学者，香港裘棤基金会Fellow，意大利理论物理国际中心(ICTP)联系成员，并曾担任国家973项目混沌子课题负责人、北京物理学会理事、中国物理学会教学委员会委员、高等学校热力学与统计物理研究会副理事长、北京师范大学物理系系主任等。目前担任Chaos、Scientific Reports、Journal of Applied Nonlinear Dynamics (JAND)等国际杂志编委。主要从事非平衡与复杂系统的统计物理与非线性动力学等领域的研究工作，承担国家级项目20多项，近几年在国际刊物发表学术论著200余篇，专著5部。指导博士后2人，博士生20余人，硕士生40多人。

报告人：刘晓萌，普林斯顿大学

时间：8月21日（周五）10:30

单位：Frontiers of Physics编辑部，高教社自然科技期刊中心

参会方式：蔻享直播

直播链接：https://www.koushare.com/lives/room/038932

摘要：

Reducing the energy bandwidth of electrons in a lattice below the long-range Coulomb interaction energy promotes correlation effects. Moiré superlattices—which are created by stacking van der Waals heterostructures with a controlled twist angle—enable the engineering of electron band structure. Exotic quantum phases can emerge in an engineered moiré flat band. The recent discovery of correlated insulator states, superconductivity and the quantum anomalous Hall effect in the flat band of magic-angle twisted bilayer graphene has sparked the exploration of correlated electron states in other moiré systems. The electronic properties of van der Waals Moiré superlattices can further be tuned by adjusting the interlayer coupling or the band structure of constituent layers. Here, using van der Waals heterostructures of twisted double bilayer graphene (TDBG), we demonstrate a flat electron band that is tunable by perpendicular electric fields in a range of twist angles. Similar to magic-angle twisted bilayer graphene, TDBG shows energy gaps at the half- and quarter-filled flat bands, indicating the emergence of correlated insulator states. We find that the gaps of these insulator states increase with in-plane magnetic field, suggesting a ferromagnetic order. On doping the half-filled insulator, a sudden drop in resistivity is observed with decreasing temperature. This critical behaviour is confined to a small area in the density–electric-field plane, and is attributed to a phase transition from a normal metal to a spin-polarized correlated state. The discovery of spin-polarized correlated states in electric-field-tunable TDBG provides a new route to engineering interaction-driven quantum phases.

报告人简介：

刘晓萌，普林斯顿大学博士后，本科毕业于北京大学物理系，2019年取得哈佛大学物理博士学位。主要研究方向包括石墨烯双层系统中的库仑拖拽，激子凝聚和层间分数量子霍尔效应，以及对包含魔角石墨烯（Magic Angle Twisted Bilayer Graphene）和扭转双层石墨烯(Twisted Double Bilayer Graphene)的各种莫尔材料的量子输运和扫描探针研究。

报告人：Xinan Zhou，IAS, Princeton

时间：8月18日（周二）9:30

单位：Kavli Institute for Theoretical Sciences，UCAS

参会方式： Zoom

Online Meeting Room：https://zoom.us/j/91346726097

Meeting ID：913 4672 6097

Correlation functions are the most basic observables of CFTs, and are mapped to AdS scattering amplitudes via AdS/CFT. However, a brute force computation is notoriously difficult and has led to only a handful of results in the past 20 years. Only recently we begin to discover and appreciate the hidden structures and simplicities of these curved space amplitudes, which in many ways are reminiscent of their flat space counterparts. The goal of this talk is to give an overview of the current status of this program and introduce the modern methods. In particular, I will introduce a powerful new method that gives a closed form answer for all tree-level four-point amplitudes in theories with maximally supersymmetry. This includes IIB SUGRA on AdS5xS5 (dual to 4d N=4 SYM), and 11D SUGRA on AdS4xS7 and AdS7xS4 (respectively dual to 3d N=8 ABJM and 6d (2,0) theory). An important ingredient of this new method is the notion of maximally R-symmetry violating (MRV) amplitude. In this limit amplitudes drastically simplify and become easy to compute. I will then explain how the full amplitudes can be recovered from this limit by using symmetries, and present the general results for these theories. Along the way, I will highlight close analogies with the flat space scattering amplitudes. I will also make brief comments on various exciting extensions of this program in the future.

The talk is based on 2006. 12505 and 2006.06653, see also 1608. 06624, 1710.05923, 1712.02788, 1712.02800 for earlier developments.

更多报告信息：中国物理学会期刊网学术讲座列表