集成光学、镍基超导薄膜、配对密度波、偶极系统、富锂正极材料 | 本周物理讲座

1

报告人：Prof. Qiang-Hua Wang，Nanjing University

时间：1月6日（周二）10:00

单位：中国科学院物理研究所

地点：Rm M830, IOP-CAS

摘要:

Pair density wave (PDW) is a superconducting state with non-zero center-of-mass momentum Cooper pairing in the absence of external magnetic field. Recent experiments show signature of such an intriguing state. However, theoretical models supporting such a state are rare, since usual zero-momentum pairing or spin/charge order might overwhelm the PDW state. Here,  by state-of-art functional renormalization group, we show that a PDW state can be realized, out of competing orders, in a two-orbital kagome lattice under fairly realistic material conditions: finite-sized Fermi pockets and moderate local Coulomb interactions. The model enjoys the following key ingredients that make the PDW favorable: 1) The Bloch states on the Fermi surfaces are strongly sublattice and orbital polarized on the Fermi pockets, so that pairing between unequal sublattices, triggered by the correlation effect, is enforced to pick up a finite total momentum, while local onsite pairing is forbidden by the repulsive Coulomb interaction; 2) The Fermi surfaces avoid the van Hove singularities which would also enhance the particle-hole channels. The degenerage PDW states at three M-momenta on the Brillouine zone boundaries could linearly combine into chiral PDW states that are topologically nontrivial. We propose this model can be realized in some p- or d-orbital kagome materials such as CsCr3Sb5, and may also be simulated by cold atoms.

2

报告人：陈钢，北京大学

时间：1月6日（周二）14:00

单位：中国科学院物理研究所

地点：M830

摘要:

Dipolar interactions—ubiquitous in anisotropic magnetic systems with local moments—can dominate over exchange interactions and profoundly reshape material behavior. Their long-range, anisotropic nature enhances magnetic frustration and may stabilize exotic emergent phenomena. In this talk, we explore dipolar effects through two complementary aspects.

First, in pyrochlore quantum spin ices with dipole-octupole doublets, we examine how symmetry-enriched U(1) topological orders in Ce pyrochlore magnets may exhibit distinct experimental signatures in the classical limit: long-range dipolar interactions can endow monopoles in the dipolar spin liquid with a finite magnetic charge, while in octupolar spin liquid monopoles show vanishing magnetic charge. This perspective offers potential resolution to debates on materials like Ce₂Sn₂O₇ and informs studies of Ce/Nd pyrochlores and Er spinels. Second, in quantum regimes, we investigate how dipolar interactions on frustrated kagome lattices may support intrinsic Z₂ topological order. Described by a Z₂ lattice gauge theory, this phase hosts fractional spinon and vison excitations, with thermodynamic and spectroscopic signatures suggesting pathways for detection in systems from polar molecule simulators to rare-earth magnets such as tripod kagome materials. To summarize, these insights point to universal principles governing topological orders across energy scales, proposing anisotropic interactions on frustrated geometries as promising components for exotic emergent phenomena. This framework encourages further exploration of anisotropic magnetism in unexplored materials and quantum simulators.

报告人简介:

现任北京大学国际量子材料中心博雅特聘教授，曾在香港大学担任教授。在University of California Santa Barbara获博士学位，师从Kavli理论物理研究所Leon Balents院士。研究领域主要是强关联多体理论，在量子磁性、关联电子、巡游阻挫、拓扑材料、介观物理学以及超冷原子等领域发表100余篇论文，并在培养学生和博后方面有一定的积累。2016年获崔琦Fellow，2018年获求是杰出青年学者奖。

3

报告人：聂越峰，南京大学现代工程与应用科学学院材料系

时间：1月6日（周二）15:00

单位：清华大学物理系

地点：物理楼W105会议室

摘要:

近年来，无限层（IL）与 Ruddlesden–Popper（RP）结构镍氧化物超导体系的发现备受瞩目。深入对比该体系与铜基超导体的异同，为揭示高温超导微观机制提供了新机遇。薄膜材料在该领域具有独特优势：IL 结构的超导相目前仅限于薄膜形式；RP 结构虽在块体中需高压获得超导，但通过外延应变可在薄膜中实现常压超导。这使得薄膜成为研究镍基超导输运性质及电子态的理想平台。然而，高质量薄膜的可控生长与原位表征仍面临挑战。本报告将介绍利用氧化物分子束外延（OMBE）技术实现原子级精确制备的方法，并结合原位表面处理、载流子输运调控与角分辨光电子谱（ARPES）测量等手段揭示其超导相图与能带结构，为理解镍基超导的内在机理提供关键实验证据。

报告人简介:

聂越峰，南京大学现代工程与应用科学学院材料系教授。本科与硕士毕业于中山大学物理系，2011年获美国康涅狄格大学物理学博士学位，之后进入康奈尔大学从事博士后研究工作，并于2014年底加入南京大学。主要从事功能氧化物薄膜及其物态调控方面的研究，在新型铁电、多铁及高温超导等方面做出了系列创新性成果，在Nature、Nat. Mater.、Phys. Rev. Lett.等期刊发表学术论文100余篇。

4

报告人： 马若辰，KITP@UCSB

时间：1月7日（周三）0:00

单位：中国科学院物理研究所

地点: M830

摘要:

Quantum phases at zero temperature can be defined as equivalence classes under local unitary transformations: two ground states are in the same phase if they can be transformed into each other via a local unitary circuit. In this talk, I will discuss how to generalize this circuit-based characterization of phases to systems at finite-temperature described by Gibbs states. We construct a local channel circuit that approximately transforms one Gibbs state into another provided the two are connected by a path in parameter space along which a certain correlation-decay condition holds. As an application, I will show that any system in the same thermal phase as a zero-temperature topological code coherently preserves quantum information for a macroscopically long time, establishing self-correction as a universal property of thermal phases.

报告人简介:

Dr. Ruochen Ma is a postdoctoral fellow at Kavli Institute for Theoretical Physics, UC Santa Barbara. He obtained his Ph.D. from Perimeter Institute. He is a condensed matter theorist working on topological phases of matter and quantum dynamics.

5

报告人：叶益聪，国防科技大学空天科学学院

时间：1月7日（周三）14:30

单位：中国科学院物理研究所
腾讯会议：895-954-791

会议密码：202601

摘要:

材料科学的传统研发范式长期面临成分与工艺空间高维、物理化学机制复杂、研发周期长、试错成本高等挑战。为应对这些挑战、突破传统研究范式的局限性，我们提出并构建了人机融合框架下大模型赋能的Al材料学家一一MatPilot。本报告将系统介绍MatPilot的整体架构，其综合运用大模型、多智能体、自动化与具身智能实验技术，以自然语言交互作为人机协作的接口，集成多种子技能，实现固相材料（以储能陶瓷为例）从自主设计到制备表征的智能研发。MatPilot是与人类智慧深度融合的“认知与执行副驾”，能“见我们所未见、知我们所不知、行我们所未行”，加速新材料的发现与创新。报告还将讨论关于“Al+材料”发展挑战特别是数据问题的思考。

报告人简介:

叶益聪，国防科技大学空天科学学院教授、博士生导师。主要从事人工智能辅助材料设计等方面的研究工作，发表论文90余篇，获军队科技进步一等奖2项、第八届材料基因高层论坛青年科学家奖一等奖，入选军队级青年人才工程，主持建成国家级一流线上课程《简明固体物理》。

6

报告人： Prof. Yusong Bai, Brown University

时间：1月8日（周四）10:00

单位：中国科学院物理研究所

地点：怀柔园区X1南楼101会议室

腾讯会议：468-247-276

摘要:

Interfaces between two-dimensional (2D) materials offer a fertile ground for emergent structures and functionalities, most notably, moiré superlattices formed in twisted bilayers that can host correlated and superconducting states. Recent studies in graphene systems have demonstrated that even richer superlattice structures and electronic behaviors can emerge in beyond-bilayer heterostructures. However, achieving such exquisite structural and interactional control in semiconducting 2D materials has remained elusive. In this talk, I will discuss two of our recent efforts to address this challenge. First, I will introduce a new excitonic material platform based on a tetralayer 2D semiconductor heterostructure that hosts a highly polarizable interlayer exciton species. In this system, the exciton dipole length, in-plane radius, and binding energy can be continuously tuned in situ over a broad range, allowing direct control over exciton–exciton interactions and the nature of excitonic many-body phase transitions. These results establish exciton geometry as a new, continuously tunable materials parameter and open pathways toward exciton-based quantum phase-transition simulators. Second, I will present our design of emergent supermoiré lattices in a hetero-tetralayer system, where two distinct yet highly interfering bilayer moiré superlattices coexist. By tuning the relative stacking order (R- vs. H-type) and twist angle between the parental bilayers, we achieve new classes of long-range supermoiré patterns that are fundamentally inaccessible in conventional bilayer systems. Together, these studies demonstrate how crafting complex 2D heterostructures enables nontrivial control over both electronic interactions and structural landscapes, offering new opportunities in quantum materials design and discovery.

报告人简介:

Yusong Bai is an Assistant Professor in the Department of Chemistry at Brown University. He received his bachelor’s degree from Beihang University in 2011, and subsequently earned his Ph.D. in Physical Chemistry from Duke University in 2017 under the supervision of Prof. Michael Therien. During his doctoral work, Yusong pioneered studies on the dynamics and spectroscopic fingerprints of trions in carbon nanotubes. Following his Ph.D., he conducted postdoctoral research at Columbia University with Prof. Xiaoyang Zhu, focusing on the spectroscopy of two-dimensional semiconductors. Yusong joined Brown University and began his independent research career in August 2022.

Yusong Bai is the recipient of multiple honors and awards, including the Petroleum Research Fund (PRF) award from the American Chemical Society, the Spectroscopy Society of Pittsburgh Award, the DARPA Advanced Research Concept Award, and the NSF Research Infrastructure Improvement Program Fellowship.

7

报告人：李彪，北京大学

时间：1月8日（周四）10:30

单位：中国科学院物理研究所

地点：怀柔园区EA楼311会议室

摘要:

传统的锂电正极材料在锂离子嵌入/脱出的过程中伴随着过渡金属阳离子的氧化还原反应，即过渡金属阳离子为氧化还原中心。近些年来，研究人员发现在富锂正极材料中阴离子可以在阳离子氧化还原的基础上进一步提供电荷转移，从而提供额外的比容量。这种阴离子氧化还原反应（anionic redox）因此成为目前的研究热点。然而，阴离子氧化还原反应同时也会带来电压滞后和较差的动力学等缺点，严重制约了材料的实际应用前景。同时阴离子氧化还原反应过程中其电荷的转移机制尚不明确，这对于如何进一步基于其设计高比容量材料提出了挑战。基于一系列富锂无序岩盐相化合物，我们发现其阴离子氧化还原过程中表现出极大的电压滞后的根本原因是由于O的电子转移因涉及到较大的局域结构扭曲而具有非常缓慢的动力学，这造成电子优先从金属的d轨道中转移出去，产生过渡金属中间体，最后金属中间体从O2-获取电子，完成O2-的氧化过程，即所谓的配体到金属的电荷转移过程（LMCT）。该发现为进一步理解富锂正极材料中的奇异现象提供了基础，且为设计高能量密度电极材料提供了思路。基于此，我们进一步设计了“富锂富镍”和“富锂中镍”相关的新型正极材料，为阴离子氧化还原开辟了实际应用的可能性。

报告人简介:

李彪，北京大学材料科学与工程学院助理教授，研究员，博士生导师。2012和2017年于北京大学分别获学士学位和博士学位，博士导师为夏定国教授。2019年至2022年于法国法兰西学院Jean-Marie Tarascon教授课题组从事博士后研究。2023年加入北京大学材料科学与工程学院。主要研究方向为锂离子电池正极材料及全固态电池。迄今为止在Nature Materials、Nature Chemistry、Advanced Materials、 Journal of American Chemical Society和Energy & Environmental Science等国际知名期刊上发表SCI论文50余篇，专著或章节2部，申请和授权专利7项。主持国家自然科学基金重大研究计划培育、面上项目、青年项目以及博士后创新人才支持计划项目等。

8

报告人：Xinwu Cao，浙江大学

时间：1月8日（周四）15:30

单位：北京大学物理学院

地点：KIAA-auditorium

摘要：

The short-timescale variability of tidal disruption events (TDEs) and changing-look active galactic nuclei (AGN) provides an ideal laboratory for studying the evolution of black hole accretion disks and coronae. We developed a black hole accretion disk-corona model, and the disk-corona evolution is derived by fitting the multi-epoch X-ray spectra of TDEs. Its evolutionary characteristics are similar to AGNs, which may help understand the physics of the accretion disk corona surrounding supermassive black holes. When a CLAGN is in its low state, a hot accretion flow (similar to a hot corona) surrounds its central black hole. The hot accretion flow is suppressed to a cold accretion disk in the high state of the CLAGN. We studied the cooling process of the hot accretion flow to form a cold accretion disk, and found that the timescale of accretion mode transition ranges from several years to decades, which is consistent with the observations. We pointed out that this mechanism provides a new approach to solving the short-timescale variability problem of CLAGNs.

报告人简介:

Xinwu Cao is a professor in School of Physics, Zhejiang University. He got his Ph. D degree from the University of Science and Technology of China in 1994. During 1999-2019, he was a research professor in Shanghai Astronomical Observatory, Chinese Academy of Sciences. He moved to Zhejiang University in 2019. His main research interests are the theories of the black hole accretion disks/outflows, and their applications in the black hole X-ray binaries and active galactic nuclei.

9

报告人：王剑威，北京大学物理学院

时间：1月8日（周四）16:00

单位：清华大学物理系

地点：物理楼W101

摘要：

本报告介绍集成光量子芯片的器件物理与关键技术，及其在量子计算与量子网络的前沿应用。包括：量子器件方面，介绍复杂量子纠缠态的光芯片上制备与量子调控、大规模光量子芯片加工与操控；量子计算方面，介绍可编程玻色取样专用光量子计算芯片、面向通用量子计算的离散变量与连续变量纠缠簇态、基于图论架构的光量子计算芯片；量子网络方面，介绍基于混合复用技术的多芯片量子纠缠网络和量子密钥分发网络；量子拓扑光学方面，介绍基于光学反常弗洛凯拓扑绝缘体的量子纠缠、非线性诱导的快速非厄米拓扑动力学相变、以及完全可编程的拓扑光子芯片等。

报告人简介:

王剑威，北京大学物理学院教授。研究领域为集成量子光学，光量子芯片物理、技术与应用，包括关键集成量子器件与硬件、大规模硅基集成光量子芯片等，并开展量子计算、量子模拟和量子网络等前沿应用的研究。在Science、Nature、Nature Physics、Nature Photonics、Nature Materials、PRL等国际学术期刊上发表论文50余篇。曾获得杨振宁奖(C.N. Yang Award)、王大珩光学奖、饶毓泰基础光学奖、北京市中关村杰出青年奖、首届腾冲青年科学家奖等。

10

报告人：Dr. Yuchi He，Ghent University; Visiting Researcher at the University of Oxford

时间：1月12日（周一）10:00

单位：中国科学院物理研究所

地点：M830

摘要:

We investigate the quantum phases of higher-spin Kitaev models using advanced tensor network methods. By boosting the performance of gradient optimization of dense infinite projected entangled pair states (iPEPS) to bond dimensions beyond D>10 and environment dimensions \chi>500, and combining novel data analysis techniques, we uncover a new phase of matter in frustrated Kitaev-type magnets: a spontaneous valence-bond solid with topological order. For spin-1, spin-3/2, and spin-2 Kitaev models, we find distinct valence-bond ordered phases characterized by translational symmetry breaking with tripled unit cells. These phases correspond to plaquette order, topological dimer order, and non-topological dimer order, respectively. Our conclusions are supported by a cross-validation between unrestricted variational tensor network calculations and the detection of symmetry breaking via cat-state behavior in symmetry-restricted states. The origin of the different orders can also be understood from theoretical analysis. This work sheds light on the interplay between topological and symmetry-breaking orders and their detection using tensor network approaches.

报告人简介:

Dr. Yuchi He obtained his PhD in Physics from Carnegie Mellon University in 2020 and his BS from Peking University. He has held postdoctoral positions at RWTH Aachen University and the University of Oxford, and is currently a postdoctoral researcher at Ghent University and a visiting researcher at Oxford. His research interests focus on strongly correlated quantum many-body systems, explored using effective field theories and tensor network methods, with recent interests in twisted transition metal dichalcogenides and frustrated magnetism.

封面图片来源：https://news.pku.edu.cn/jxky/80b2d264b7e849adb7955a20e029148c.htm

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