集成光學、鎳基超導薄膜、配對密度波、偶極系統、富鋰正極材料 | 本周物理講座

1

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

時間：1月6日（周二）10:00

單位：中國科學院物理研究所

地點：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

報告人：陳鋼，北京大學

時間：1月6日（周二）14:00

單位：中國科學院物理研究所

地點：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 Ce?Sn?O? 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 Z? topological order. Described by a Z? 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.

報告人簡介:

現任北京大學國際量子材料中心博雅特聘教授，曾在香港大學擔任教授。在University of California Santa Barbara獲博士學位，師從Kavli理論物理研究所Leon Balents院士。研究領域主要是強關聯多體理論，在量子磁性、關聯電子、巡游阻挫、拓撲材料、介觀物理學以及超冷原子等領域發表100余篇論文，并在培養學生和博后方面有一定的積累。2016年獲崔琦Fellow，2018年獲求是杰出青年學者獎。

3

報告人：聶越峰，南京大學現代工程與應用科學學院材料系

時間：1月6日（周二）15:00

單位：清華大學物理系

地點：物理樓W105會議室

摘要:

近年來，無限層（IL）與 Ruddlesden–Popper（RP）結構鎳氧化物超導體系的發現備受矚目。深入對比該體系與銅基超導體的異同，為揭示高溫超導微觀機制提供了新機遇。薄膜材料在該領域具有獨特優勢：IL 結構的超導相目前僅限于薄膜形式；RP 結構雖在塊體中需高壓獲得超導，但通過外延應變可在薄膜中實現常壓超導。這使得薄膜成為研究鎳基超導輸運性質及電子態的理想平臺。然而，高質量薄膜的可控生長與原位表征仍面臨挑戰。本報告將介紹利用氧化物分子束外延（OMBE）技術實現原子級精確制備的方法，并結合原位表面處理、載流子輸運調控與角分辨光電子譜（ARPES）測量等手段揭示其超導相圖與能帶結構，為理解鎳基超導的內在機理提供關鍵實驗證據。

報告人簡介:

聶越峰，南京大學現代工程與應用科學學院材料系教授。本科與碩士畢業于中山大學物理系，2011年獲美國康涅狄格大學物理學博士學位，之后進入康奈爾大學從事博士后研究工作，并于2014年底加入南京大學。主要從事功能氧化物薄膜及其物態調控方面的研究，在新型鐵電、多鐵及高溫超導等方面做出了系列創新性成果，在Nature、Nat. Mater.、Phys. Rev. Lett.等期刊發表學術論文100余篇。

4

報告人： 馬若辰，KITP@UCSB

時間：1月7日（周三）0:00

單位：中國科學院物理研究所

地點: 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.

報告人簡介:

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

報告人：葉益聰，國防科技大學空天科學學院

時間：1月7日（周三）14:30

單位：中國科學院物理研究所
騰訊會議：895-954-791

會議密碼：202601

摘要:

材料科學的傳統研發范式長期面臨成分與工藝空間高維、物理化學機制復雜、研發周期長、試錯成本高等挑戰。為應對這些挑戰、突破傳統研究范式的局限性，我們提出并構建了人機融合框架下大模型賦能的Al材料學家一一MatPilot。本報告將系統介紹MatPilot的整體架構，其綜合運用大模型、多智能體、自動化與具身智能實驗技術，以自然語言交互作為人機協作的接口，集成多種子技能，實現固相材料（以儲能陶瓷為例）從自主設計到制備表征的智能研發。MatPilot是與人類智慧深度融合的“認知與執行副駕”，能“見我們所未見、知我們所不知、行我們所未行”，加速新材料的發現與創新。報告還將討論關于“Al+材料”發展挑戰特別是數據問題的思考。

報告人簡介:

葉益聰，國防科技大學空天科學學院教授、博士生導師。主要從事人工智能輔助材料設計等方面的研究工作，發表論文90余篇，獲軍隊科技進步一等獎2項、第八屆材料基因高層論壇青年科學家獎一等獎，入選軍隊級青年人才工程，主持建成國家級一流線上課程《簡明固體物理》。

6

報告人： Prof. Yusong Bai, Brown University

時間：1月8日（周四）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：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.

報告人簡介:

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

報告人：李彪，北京大學

時間：1月8日（周四）10:30

單位：中國科學院物理研究所

地點：懷柔園區EA樓311會議室

摘要:

傳統的鋰電正極材料在鋰離子嵌入/脫出的過程中伴隨著過渡金屬陽離子的氧化還原反應，即過渡金屬陽離子為氧化還原中心。近些年來，研究人員發現在富鋰正極材料中陰離子可以在陽離子氧化還原的基礎上進一步提供電荷轉移，從而提供額外的比容量。這種陰離子氧化還原反應（anionic redox）因此成為目前的研究熱點。然而，陰離子氧化還原反應同時也會帶來電壓滯后和較差的動力學等缺點，嚴重制約了材料的實際應用前景。同時陰離子氧化還原反應過程中其電荷的轉移機制尚不明確，這對于如何進一步基于其設計高比容量材料提出了挑戰。基于一系列富鋰無序巖鹽相化合物，我們發現其陰離子氧化還原過程中表現出極大的電壓滯后的根本原因是由于O的電子轉移因涉及到較大的局域結構扭曲而具有非常緩慢的動力學，這造成電子優先從金屬的d軌道中轉移出去，產生過渡金屬中間體，最后金屬中間體從O2-獲取電子，完成O2-的氧化過程，即所謂的配體到金屬的電荷轉移過程（LMCT）。該發現為進一步理解富鋰正極材料中的奇異現象提供了基礎，且為設計高能量密度電極材料提供了思路。基于此，我們進一步設計了“富鋰富鎳”和“富鋰中鎳”相關的新型正極材料，為陰離子氧化還原開辟了實際應用的可能性。

報告人簡介:

李彪，北京大學材料科學與工程學院助理教授，研究員，博士生導師。2012和2017年于北京大學分別獲學士學位和博士學位，博士導師為夏定國教授。2019年至2022年于法國法蘭西學院Jean-Marie Tarascon教授課題組從事博士后研究。2023年加入北京大學材料科學與工程學院。主要研究方向為鋰離子電池正極材料及全固態電池。迄今為止在Nature Materials、Nature Chemistry、Advanced Materials、 Journal of American Chemical Society和Energy & Environmental Science等國際知名期刊上發表SCI論文50余篇，專著或章節2部，申請和授權專利7項。主持國家自然科學基金重大研究計劃培育、面上項目、青年項目以及博士后創新人才支持計劃項目等。

8

報告人：Xinwu Cao，浙江大學

時間：1月8日（周四）15:30

單位：北京大學物理學院

地點：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.

報告人簡介:

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

報告人：王劍威，北京大學物理學院

時間：1月8日（周四）16:00

單位：清華大學物理系

地點：物理樓W101

摘要：

本報告介紹集成光量子芯片的器件物理與關鍵技術，及其在量子計算與量子網絡的前沿應用。包括：量子器件方面，介紹復雜量子糾纏態的光芯片上制備與量子調控、大規模光量子芯片加工與操控；量子計算方面，介紹可編程玻色取樣專用光量子計算芯片、面向通用量子計算的離散變量與連續變量糾纏簇態、基于圖論架構的光量子計算芯片；量子網絡方面，介紹基于混合復用技術的多芯片量子糾纏網絡和量子密鑰分發網絡；量子拓撲光學方面，介紹基于光學反常弗洛凱拓撲絕緣體的量子糾纏、非線性誘導的快速非厄米拓撲動力學相變、以及完全可編程的拓撲光子芯片等。

報告人簡介:

王劍威，北京大學物理學院教授。研究領域為集成量子光學，光量子芯片物理、技術與應用，包括關鍵集成量子器件與硬件、大規模硅基集成光量子芯片等，并開展量子計算、量子模擬和量子網絡等前沿應用的研究。在Science、Nature、Nature Physics、Nature Photonics、Nature Materials、PRL等國際學術期刊上發表論文50余篇。曾獲得楊振寧獎(C.N. Yang Award)、王大珩光學獎、饒毓泰基礎光學獎、北京市中關村杰出青年獎、首屆騰沖青年科學家獎等。

10

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

時間：1月12日（周一）10:00

單位：中國科學院物理研究所

地點：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.

報告人簡介:

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.

封面圖片來源：https://news.pku.edu.cn/jxky/80b2d264b7e849adb7955a20e029148c.htm

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