磁制冷、拓扑量子流体、铁电薄膜的光电效应、费米气体 | 本周物理讲座

1

报告人：Tomoaki Yamada，Nagoya University

时间：8月27日（周二）10:00

单位：中国科学院物理研究所

地点：A332会议室

摘要：

In this presentation, we first show the EO property in classical ferroelectric thin films having perovskite structure, including the strain effect and the domain switching contribution. Then, we explore the EO response in emerging ferroelectric thin films, having fluorite and wurtzite structures, which are better compatible with CMOS technology.

Classical ferroelectric thin films: We experimentally clarified that the EO response of compressively strained BST thin films was enhanced toward the phase transition temperature modified by the strain (Fig. (a)). The theoretical prediction based on a phenomenological thermodynamic model also supported the experimental result. We also found that the single c-domain PZT films show the EO response smaller than the most of reported EO responses for multidomain PZT films, indicating that the large EO response reported for PZT films mostly arises from the extrinsic domain switching by the applied voltage.

Emerging ferroelectric thin films: We found the evident linear EO response in Y-doped HfO2, Sc-doped AlN, and Mg-doped ZnO thin films, which indicates that those EO response originates from the spontaneous polarization in the films. Especially, the EO coefficient of Mg-doped ZnO thin films was remarkably enhanced with increasing Mg content and reached 7.6 pm/V, which is over three times larger than the reported values for ZnO-based thin films and over twice larger than that of ZnO single crystals (Fig. (b)).

报告人简介：

Tomoaki Yamada received his B.S. degree in Inorganic Materials and Ph.D. degree in Material Science and Engineering from Tokyo Institute of Technology, Japan, in 1999 and 2003, respectively. In 2004, he joined the Ceramics Laboratory of the Swiss Federal Institute of Technology at Lausanne (EPFL), Switzerland, where he worked in the field of ferroelectric thin films. In 2008, he became an assistant professor under the Global COE Program in Tokyo Institute of Technology. In 2010, he moved to Nagoya University, Japan, as an associate professor, and was promoted to a full professor in 2021. From 2010 to 2020, he held a concurrent researcher position in the JST-PRESTO program for developing novel piezoelectric nanostructures and energy harvesters. Currently, he is also a visiting professor of MDX Research Center for Element Strategy at Tokyo Institute of Technology. His domains of experience and expertise are functional metal oxide (dielectric/piezoelectric/ferroelectric) thin films and devices, especially with focus on the manipulation of epitaxial growth, nano-structured interfaces, and characterizations and applications of these hetero-structures. He received the Richard M. Fulrath Award of the American Ceramic Society in 2020 for his achievements so far. He is also a fellow of the Ceramic Society of Japan.

2

报告人：罗鑫宇，马普量子光学研究所

时间：8月27日（周二）10:00

单位：中国科学院理论物理所

地点：南楼6620

摘要：

Microwave-shielding has proven to be a powerful technique for producing degenerate quantum gases of polar molecules as well as assembling ultracold polyatomic molecules. Here, I will review our efforts in controlling the interactions of ultracold molecules using microwave fields, enabling us to stabilize the molecular gases and evaporate them to temperatures well below the Fermi temperature. The shape, symmetry, and depth of the intermolecular potential can be flexibly controlled by the polarization, strength, and frequency of the microwave field. This is a unique feature of microwave-shielded polar molecules that is distinguished from ultracold atoms. It allows us to observe field-linked resonances in collisions of polar molecules, providing a universal tool for independently controlling the dipolar and contact interactions of molecules, as well as creating exotic long-range tetratomic molecules. In the end, I will discuss the perspectives of a p-wave superfluid of dimers and its crossover to a Bose-Einstein condensate of tetramers.

报告人简介：

Xin-Yu Luo is an independent research group leader at the Max-Planck-Institute for Quantum Optics. He has been focusing on experiments of quantum manipulation and precision measurements with ultracold atoms and polar molecules. His current research interest is to understand and control the collisions of ultracold polar molecules and, subsequently, investigate strongly interacting dipolar quantum many-body systems.

3

报告人：王根，Aix Marseille University

时间：8月27日（周二）12:00

单位：中国科学院理论物理研究所

地点：南楼6620

摘要：

I will present the latest calculation of HVP contributions to muon anomaly with Lattice QCD from Budapest-Marseille-Wuppertal collaboration (BMWc). The result leads to a prediction 714.1(2.2)(2.5)[3.3]x10-10 that differs from the experimental measurement of a_μ by only 0.9 standard deviations. This provides a remarkable validation of the standard model to 0.37 ppm. Since the largest systematic uncertainty comes from the ratio between the intrinsic QCD scale and fermion masses, we measure the precise Ω baryon mass in lattice units at seven lattice spacings down to a=0.048 fm with N_f=2+1+1 staggered quarks, including QED and strong-isospin corrections. We perform these measurements by solving the Generalized Eigenvalue Problem, adapted to staggered fermions to fully resolve the negative parity and excited states. The most precise intrinsic QCD scale parameter  w_0=0.17245(22)(46)[51] fm in the continuum limit at physical quark masses is determined using the physical Ω baryon mass, with unprecedented 0.3 percent precision.

报告人简介：

Dr. Gen Wang graduated from University of Kentucky, US and current postdoc at Aix Marseille University, France under Budapest-Marseille-Wuppertal collaboration. His main research interest is on high-precision lattice calculation of the hadron structure, such as muon anomalous magnetic moment, proton spin decompositions and standard model parameter determinations.

4

报告人：Prof. Hartmut Löwen，Institute of Theoretical Physics II: Soft Matter, Heinrich Heine University of Düsseldorf, Germany

时间：8月27日（周二）14:00

单位：中国科学院物理研究所

地点：M楼249会议室

摘要：

While ordinary materials are typically composed of inert "passive" particles, active matter comprises objects or agents which possess an intrinsic propulsion. Examples are living systems like schools of fish, swarms of birds, pedestrians, and swimming microbes but also artificial particles equipped with an internal motor such as robots and colloidal Janus particles. Active matter is praised for possible technological applications ranging from micro-surgery to environmental cleaning.

This talk provides an introduction to the basic physics of active matter with an emphasis on the statistical mechanics of synthetic artificial self-propelled particles. After an introduction of basic concepts to describe self-propelled colloids in the mesoscopic soft matter regime, such as active Brownian motion, novel collective phase transitions are described including motility-induced phase separation of repulsive self-propelled particles. Then the importance of inertia relevant for particles of larger size is discussed. Finally, two possible paths to next-generation active materials are pointed out: either functionalized microswimmers equipped with artificial intelligence or ultracold atoms in optical fields opening the door to the new field of quantum active matter.

报告人简介：

Hartmut Löwen studied physics, mathematics, and chemistry at the University of Dortmund in Germany, where he obtained his PhD in physics in 1987. After postdoctoral research stays at Ludwig Maximilians University of Munich with Herbert Wagner and at Ecole Normale Supérieure de Lyon with Jean-Pierre Hansen, he accepted the call as a chair professor at the University of Düsseldorf in 1995.

Prof. Löwen has significantly contributed to theoretical physics with over 500 publications to date, with a current h-index of over 90. He is recognized as one of the leading figures in the fields of soft and active matter. He pioneered the physics of passive and self-propelled colloids and contributed to the research field of active matter exploring phenomena like motility-induced phase transitions, active turbulence, chirality and non-reciprocal interactions. During his career he has received multiple prizes and awards, most notably Heisenberg Fellowship and the Gerhard Hess Research Prize by the German Research Foundation, the joint Gentner-Kastler Prize of the German Physical Society and French Physical Society, medal of honor of Heinrich Heine University of Düsseldorf, and SigmaPhi Prize for his contributions to statistical physics and soft matter.

5

报告人：Dr. Ir. Keerthivasan Rajamani，University of Twente, Dept. Thermal and Fluid Engineering

时间：8月27日（周二）16:30

单位：中国科学院物理研究所

地点：物理所M255

摘要：

Magnetic refrigeration is considered as a potential alternative to vapour compression refrigeration technology due to its relatively higher energy efficiency and its use of environment-friendly materials. A magnetocaloric refrigerator with no moving parts offers higher reliability for critical applications and lower vibration. For this a mixture of magnetocaloric material and heat transfer liquid as the refrigerant is considered. This mixture is circulated between hot and cold heat exchangers using a ferrohydrodynamic pump, while the permanent magnet is stationary. It is analysed by first considering the ferrohydrodynamic pump design, followed by material analysis of the mixture, and finally a system level analysis of the refrigerator. For the ferrohydrodynamic pump, a novel design that achieves the same normalized mass flow rate as the state-of-the-art, but at three orders of magnitude lower frequencies is experimentally tested and numerically characterized.  For the material analysis, La(Fe,Mn,Si)13Hz with Ga-In-Sn liquid metal is considered owing to the favourable thermal and fluid properties of the latter, and their compatibility over 1.5 years is analysed.  Finally, numerical analysis on the system level performance is performed for different heat transfer fluid, volume fraction of magnetocaloric material, mass flow rate of the mixture, while their cooling power and second-law efficiency are determined.

6

报告人：Prof. Hartmut Löwen，Heinrich Heine University of Düsseldorf

时间：8月28日（周三）10:00

单位：中国科学院理论物理研究所

地点：南楼6620

摘要：

In this talk we shall discuss the impact of non-reciprocal interactions on collectiven onequilibrium phenomena. We start with the case of constant nonreciprocity where an exact mapping of an equilibrium system is possible albeit with different kinetictemperatures. This prediction was confirmed in experiments on complex plasmas under ion flow with non-reciprocal wake charges. Overdamped dynamics with nonreciprocity leads to diferent behaviors where various nonequilibrium phases were discovered. Then a novel generic field theory will be proposed, termed Active Model N where N stands for nonreciprocity. This theory is derived from particle-resolved Langevin dynamics and its numerical implementation leads to new patterns termed “active yarn". Finally we shall describe an example for nonreciprocal interactions in the animal kingdom, namely swarms of zebra fish, where we demonstrate evidence that already three fish show characteristics of a full swarm.

报告人简介：

Dr. Hartmut Lowen obtained his PhD in physics at the University of Dortmund in Germany in 1987. After postdoctoral research stays at Ludwig Maximilians University of Munichwith Herbert Wagner and at Ecole Normale Supérieure de Lyon with Jean-Pierre Hansenhe，worked as a professor at Heinrich Heine University of Düsseldorf in 1995. He is recognized as one of the leading figures in the fields of soft and active matter. During his career he has received multiple prizes and awards, such as Heisenberg Fellowship and the Gerhard Hess Research Prize by the German Research Foundation, the joint Gentner-Kastler Prize of the German Physical Society and French Physical Society, medal of honor of Heinrich Heine University of Düsseldorf, SiamaPhi Prize, etc.

7

报告人：许群，郑州大学河南先进技术研究院

时间：8月28日（周三）15:00

单位：中国科学院物理研究所

地点：A楼232会议室

摘要：

超临界CO2对层内化学键的调控主要体现在其可以破坏层内共价键，打乱原子排列，导致晶格畸变，使材料非晶化，引入缺陷，或使多种材料之间成键构筑异质结构。

我们利用超临界CO2自上而下制备了不同形态和结构的二维材料、二维非晶材料及其异质结结构。实验结果表明超临界CO2吸附在材料的表面抑制了其各向异性生长，形成了二维纳米片的结构，也因此抑制了二维纳米片的结晶动力学，使样品呈现非晶态结构。实验结果表明利用超临界CO2可以控制二维结构的形貌演化，从而抑制了层间原子有序排列。此外，超临界CO2在层状材料层内会引入缺陷，超临界CO2与材料之间的相互作用包括化学键的断裂或化学吸附和解吸来引入缺陷，缺陷的形成导致相邻晶格畸变和结构转变；另一方面，超临界CO2诱导的剪切应力会促进局部剪切变形和原子重排，从而导致剪切带和位错等大尺寸缺陷。由于理论研究发现二维（2D）材料比体相有着更高的平均磁矩和更大的磁各向异性，因而在磁性器件应用上拥有更多优势。借助于CO2精准调控固体物质的化学组成、相态、晶体结构及其关联的化学有序和电荷有序，我们进一步研究了材料室温铁磁性质。

报告人简介：

许群教授，1999年9月博士毕业于中国科学院化学研究所，2001年7月完成德国Karlsruhe研究中心博士后工作。同年回国，应聘到郑州大学，组建了郑州大学绿色化学功能材料实验室。现任河南先进技术研究院执行院长，教授，博士生导师。已在国内国际学术期刊上发表SCI学术论文200多篇，授权国家发明专利20项，2008年获中国青年女科学家奖提名奖，2009年获国务院政府特殊津贴2009年获日本化学会青年学者奖。

8

报告人：Prof. Luc Bergé，CELIA, Université de Bordeaux-CNRS-CEA

时间：8月29日（周四）10:30

单位：中国科学院物理研究所

地点：M249会议室

摘要：

Terahertz (THz) waves are nowadays very popular because of their numerous applications, for example in security screening, medical imaging, time-domain spectroscopy and remote detection. At non-relativistic laser intensities, air plasmas created by two-color optical pulses supply suitable THz emitters free of any damage. Their “photocurrents” generate ultrabroadband terahertz radiations which find direct applications in the coherent spectroscopy of macromolecules. At relativistic intensities, gas plasmas develop nonlinear electrostatic fields used in laser-wakefield particle acceleration. Accelerated electrons crossing the plasma-vacuum interface then emit coherent transition radiation (CTR) associated with tens of GV/m THz field amplitude and mJ energy. CTR also operates in relativistic laser-solid interactions, whereby it benefits from a stronger absorption of the laser energy into MeV-range electrons. Yet, the hot-electron population does not only radiate via CTR when exiting a solid foil. Less energetic electrons actually get reflected in the strong charge-separation field set up in vacuum. This results in an additional coherent, synchrotron-type radiation of polarity opposite to that of CTR. Moreover, the sheath electric field induced by the hot electrons subsequently sets into motion the surface ions over picosecond timescales and lead to a dipole-type, low-frequency radiation contributing to the THz spectrum.

This talk will first address the key role of photocurrents in the creation of broadband terahertz pulses at moderate laser intensities. Recent experimental results on plasma-based THz molecular spectroscopy will be discussed. Using multi-dimensional particle-in-cell simulations we will next present new perspectives in the production of ultra-intense terahertz pul

9

报告人：杨波，Nanyang Technological University

时间：8月30日（周五）15:00

单位：清华大学物理系

地点：理科楼C302

摘要：

The fractional quantum Hall (FQH) effect realized in Landau levels is a family of strongly correlated topological quantum fluids in two-dimension, with exotic low lying charge excitations that are anyonic and even non-Abelian. Here we propose a unified framework in understanding the integer and fractional quantum Hall systems via Hilbert space truncation, so that these quantum fluids consist of “elementary particles” emerging from special“2D universes” with conformal symmetry. Interestingly, the hierarchical structure of these 2D conformal universes (or conformal Hilbert spaces) allows us to reveal internal structures of anyons of the FQH phases (e.g. the Laughlin and Moore-Read phases), and to derive experimentally relevant conditions for such anyons or quasiholes to undergo fractionalisation within the same topological phase. We will also discuss about the long wavelength neutral excitations analogous to the spin-2 graviton and higher-spin-mode in these topological quantum fluids. The former has been recently measured with Raman scattering, and we propose possible ways of detecting higher spin modes with multi-photon processes or Laguerre-Gaussian beam in experiments.

报告人简介：

Assistant Professor Yang Bo obtained his Bachelor’s degree in Science from Stanford University, and PhD from Princeton University. He is the research scientist from 2014 to 2018 at the Institute of High Performance Computing under A*STAR, focusing on non-linear dynamics, complex systems and traffic flow modelling/simulation. He joined the Nanyang Technological University as an assistant professor with the National Research Foundation Fellowship in 2020. Dr. Yang Bo is interested in emergent behaviours from both classical and quantum many body systems, with a particular focus on fractional quantum Hall and anomalous quantum Hall effect and topological materials.

10

报告人：Prof. Dr. Matthias Schott，University of Bonn

时间：8月30日（周五）15:00

单位：李政道研究所

链接：

摘要：

The field of axion physics has garnered significant attention in recent years. This is not only due to the absence of evidence for new heavy elementary particles, but also because the category of axion-like particle could elegantly account for several of our key observations, such as dark matter. In this presentation, I will provide an overview of the ongoing and forthcoming experimenta endeavors aimed at detecting axions and. more broadly, axion-like particles, with a particular emphasis on searches conducted at the LHC, While we have not vet discovered any evidence of axion-like particles, these experiments may enable us to explore high.frequency gravitational waves, which will also be briefly discussed.

报告人简介：

Matthias Scott, a distinguished particle physicist, earned his Ph.D. in Physics from Ludwig-Maximilian University in 2007. He has been recognized with numerous awards for his influential research contributions, including the Alexander von Humboldt Foundation's Henriette Herz Scout Award in January 2020. which is highly regarded within the international scientific community He currently serves as a Full Professor at the University of Bonn. Germany. aposition he has held since 2024. Prior to this, he was a Full Professor at the University of Mainz, Germany, from 2019 to 2023, In his current role at the University of Bonn, Scott focuses on precision measurements, collider-based axion searches, and gravitational wave experiments, During his time at the University of Mainz, his research encompassed electroweak interactions at the LHC, the development of Micromegas detectors, and ATLAS muon upgrades Professor Scott's extensive body of work not only deepens out understanding of particle physics but also propels the advancement of technology utilized in experimental physics.

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