基于重离子储存环原子核质量精确测量 | 本周物理学讲座
报告人：张玉虎，中科院近代物理研究所
时间：11月06日（周三）15:30
单位：北京航天航空大学
地点：北校区沙河主楼C座511会议室
国家大科学装置重离子储存环CSR的建成并投入运行为核物理基础及应用研究提供了一个先进的科研平台。最近几年，我们在CRS上建立了等时性核质量测量装置，以中科院近代物理研究所的科研人员为主,通过国际合作,对短寿命原子核的质量进行一系列实验测量,得到了新的或更高精度的数据,基于此,对核结构及核天体物理中的前沿科学问题进行了研究。本报告将介绍上述工作以及将来的研究计划。
2 Vacancy-driven strange metal physics in transition metal rutile nanostructures
报告人：Juhn-Jong Lin，National Chiao Tung University, Taiwan
时间：11月05日（周二）10:30
单位：中科院物理所
地点：M楼253
Metal physics beyond the Landau Fermi liquid paradigm is a central topic in contemporary condensed matter science. Its connection with unconventional superconductivity is experimentally well established but the conditions under which these enigmatic metals can form has remained perplexing. The routes proposed towards strange metal formation, which includes the two-channel Kondo effect, generally require rather special conditions or fine tuning. Here we report the observation of robust vacancy-driven orbital two-channel Kondo behavior which occurs without fine-tuning, in paramagnetic IrO2 nanowires possessing the rutile structure. We further demonstrate tunability of this unconventional state to its Fermi-liquid counterpart within the rutile structure through a complementary analysis of antiferromagnetic RuO2 nanowires. Our findings establish the inherent occurrence of non-Fermi liquid physics in a class of topological quantum materials, with implications for fundamental research and potential quantum device applications.
3 Intertwined Orders in the Cuprate Superconductor and the Underlying Organization Principle
报告人：翁征宇，清华大学高等研究院
时间：11月06日（周三）14:00
单位：中科院物理所
地点：M楼234
A sensible phenomenology of the complex phase diagram and rich phenomenon in the high-Tc cuprate calls for a microscopic understanding based on general principles. In this talk, I will identify a set of the most essential organization principles for the doped Mott insulator, which are argued to have captured the fundamental physics of the cuprate superconductor. Then I will exemplify their nature as the exotic long-range entanglement of many-body quantum mechanics by using the exact numerical tools of exact diagonalization and density matrix renormalization group, which are applied to some special cases of finite size/limited geometry to demonstrate the consequences of the general principle. Next, I will focus on the phase diagram relevant to the experiments in the cuprate, and show that it may be unified by a “parent”ground state ansatz constructed based on the organization principles. Here the superconducting state is of non-BCS nature with modified London equation and new elementary excitations. In particular, the two-gap structure and dichotomy between the nodal and antinodal regimes in the superconducting state, the origin of Fermi arc in the pseudogap regime, and the strange metal behavior in the high-temperature regime will be discussed as part of the emergent phenomenon.
报告人：Chi-Ming Chang (张其明)，YMSC, Tsinghua
时间：11月06日（周三）14:00
单位：中科院理论物理所
地点：ITP South Building 6420
Melonic tensor model is a new type of solvable model, where the melonic Feynman diagrams dominate in the large N limit. The melonic dominance, as well as the solvability and the IR stability of the model, relies on a special type of interaction vertex, which generically would not be preserved under renormalization group flow. I will discuss a class of 2d N=(2,2) melonic tensor models, where the non-renormalization of the superpotential protects the melonic dominance. Another important feature of our models is that they admit a novel type of deformations which gives a large IR conformal manifold. At generic point of the conformal manifold, all the flavor symmetries (including the O(N)^{q-1} symmetry) are broken and all the flat directions in the potential are lifted. I will also discuss how the operator spectrum and the chaos exponent depend on the deformation parameters.
5The Role of Transition Dipole Moment in Photocatalysis and Strong Laser Field Driven Dynamics
报告人：陆瑞锋，南京理工大学
时间：11月06日（周三）15:10
单位：北京大学
地点：物理楼中楼212教室
The electronic band structure and optical property calculations help us to find new photocatalysts with visible light response in theory. However, the appropriate band gap and band alignment sometimes do not mean better light absorption properties. With the help of detailed transition dipole moment analysis, we can clearly reveal the catalytic mechanism of photocatalytic water splitting. In addition, our theoretical simulations show that the amplitude and phase of transition dipole moments play an important role in the attosecond transient absorption spectra of atomic systems and the high-order harmonic spectra of crystal systems under ultrafast intense laser irradiation.
报告人：Jinfeng Jia，Shanghai Jiao Tong University
时间：11月07日（周四）15:30
单位：清华大学
地点：理科楼郑裕彤讲堂
Recently, quantum materials are the hottest topic in condensed matter physics. As the samples become smaller and smaller, in situ characterizations become more and more important. By combining molecular beam epitaxy (MBE) with STM, ARPES and other techniques, in situ characterizations can be achieved. With atomic precision control of growth, MBE can provide clean and smooth surfaces for STM and ARPES to study. Meanwhile, STM, ARPES and in situ techniques can also provide enough information for MBE to eliminate much of the trial and error during growth, so that one can fabricate the structures that do not exist in nature or cannot be grown by other techniques. Therefore, this kind of combined system can do some unique work which cannot be done by separate instruments.
In this talk, I will introduce several works done with the combined system to demonstrate the strong power of the combination. With help of STM, artificial cluster crystals, i.e. a periodical array of identical nanoclusters can be grown with precise control. Atomically flat Pb thin films, stanene etc. can be grown with MBE and studied with STM. In Pb films on Si(111), we found quantum well states (QWS) form due to the electronic confinement in the film normal direction and novel properties induced by QWS. We also found high quality topological insulator films can be grown with MBE. Standing waves and Landau levels were observed with low temperature STM and demonstrated the existing of the topological surface states and the prohibition of backward-scattering. Topological insulator/superconductor hetero structures are also fabricated for exploring Majorana fermions.
7 Wideband Silicon Nanophotonics for Classical and Quantum Applications
报告人：Xiyuan Lu，NIST, University of Maryland College Park
时间：11月08日（周五）15:30
单位：北京大学
地点：物理楼中楼212教室
Recent advances in nanophotonic technology have led to major progress and new promise in wideband nonlinear optics. In this talk, I will discuss our recent efforts in exploring nonlinear nanophotonics across widely separated spectral bands from visible (~650 nm) to telecom (~1550 nm), for both classical and quantum applications. In the classical regime, efficient spectral translation of light is useful for many integrated photonics applications, including spectroscopy, sensing, and metrology, where coherent visible light needs to be generated efficiently on-chip. I will introduce our recent work1 on how to translate telecom light into the visible band by stimulated four-wave mixing, a third-order nonlinear optical process, inside a high quality factor silicon nitride microring. The translation efficiency is comparable to the best current second-order nonlinear result and is a record-high value for nanophotonic spectral translation. In the quantum regime, narrow-linewidth, wide-band quantum entanglement is particularly useful in connecting different species of trapped atoms/ions, defect centers and quantum dots to the telecommunications bands for future quantum communication systems. I will discuss our work2 in generating visible-telecom photon pairs with record-high brightness and efficiency. Time-energy entanglement is generated and then distributed over a 20 km fiber. I will also introduce our exciting new progress in both applications areas, including visible-telecom optical parametric oscillation3 and wideband quantum frequency combs.
报告人：郭奉坤，中科院理论物理研究所
时间：11月08日（周五）18:30
单位：中国科学院大学
地点：雁栖湖校区教1-108
强相互作用是自然界的基本相互作用之一。其基本理论是量子色动力学(QCD)。QCD在低能区的非微扰相互作用产生了质子、中子等色单态的强子,是宇宙可见物质绝大部分质量的来源,因此对低能QCD的物质结构的研究是极重要又极具挑战性的问题。2003年以来世界各地的高能物理实验中发现了大量新的强子态,与此前较成功的夸克势模型的预言完全不同,对它们的研究拓展了我们对于强子结构的认识。在此报告中我将介绍近年来关于强子结构的实验发现及其理论进展,包括粲介子、ⅩYZ态以及五夸克态等。
报告人：顾雪梅，南京大学
时间：11月11日（下周一）15:30
单位：北京大学
地点：物理楼中楼212教室
Experiments in laboratories are unquestionably crucial to increase our understanding of quantum systems and inspire new insights into future applications. However, results of quantum experiments are perfectly computable - but often elude human logic. In this talk, we will present a hidden bridge between quantum experiments and graph theory to show how one can model and understand modern-day photonic quantum experiments. First we will explain how questions in quantum physics can be translated and answered using Graph theory, while questions in graph theory can be converted and answered in quantum experiments. Then we introduce one important perspective is that complex weights in the graph naturally describe the quantum interference which happens when many photons are involved. This quantum interference is the basis of a new special-purpose scheme of quantum computation, which can be exploited to solve Graph Theory questions that are intractable on a classical computer. In the end, our new connection between these seemingly unrelated fields also revealed new insights into quantum state generation with current photonic technology using linear optics and probabilistic sources. In general, the bridge gives us a new perspective on photonic quantum technologies and will be significant for the design of future experiments and applications in quantum information.
更多报告信息：中国物理学会期刊网学术讲座列表
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