基于氧化物的电子突触器件及类脑计算研究||本周物理学术讲座

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基于氧化物的电子突触器件及类脑计算研究||本周物理学术讲座

2017 年 9 月 19 日 中国物理学会期刊网

1基于氧化物的电子突触器件及类脑计算研究

报告人：吴华强，清华大学微纳电子系

时间：9月21日（周四）16:00

单位：清华大学物理系

地点：理科楼郑裕彤讲堂

人工智能的研究和应用已经取得了突飞猛进的发展，但是运行人工智能深度神经网络算法的计算平台主要是超级计算机群（成百上千个CPU和GPU）,不但需要巨大的硬件投入，而且占用的空间和消耗的能源也非常可观。受限于存储计算分离对芯片性能的限制，同时CMOS工艺微缩速度放缓，以及人工智能应用对计算存储需求的不断提升，当前的技术将面临诸多新的挑战。在这一背景下，新器件的出现变得至关重要，通过引入新原理的半导体器件，不但可以拓展芯片的功能，甚至可以颠覆传统电路理论，突破当前芯片面临的能效、速度瓶颈，大幅提升芯片性能。基于过渡族金属氧化的忆阻器件显示出了优越的存算一体的特性，能够规避存储和计算之间数据搬运的功耗并且能够实现大规模集成，进而实现高性能计算。展望未来，智能社会即将来临！面向未来的智能芯片，最底层的器件需要具备哪些特性呢？

2In Situ Synchrotron XRD Studies on the Synthesis of Cathode Materials for Li-Ion Battery

报告人：Jianming Bai， Brookhaven National Laboratory

时间：9月19日（周二）10:30

单位：中科院物理研究所

地点：D楼二层210会议室

In-situ, real-time tracking of the structural chemistry evolution during the synthesis reactions can provide details on reaction process, elucidating intermediate phases and how temperature, pressure, time and the precursor concentrations affect the kinetic reaction pathways. Synchrotron X-ray powder diffraction (SXPD), with its high beam intensity and angular resolution, allows in situ structural characterization in short time scales capable of catching subtle structure changes in the materials under synthesis. The presentation will introduce the in situ SXRD techniques developed at NSLS and NSLS-II, as applied in study of synthesis processes of cathode materials for Li-ion batteries. Specific examples will be given to show how the insights gained from in-situ studies may provide guidance to rational design and synthesis of new battery materials.

3Berry Phase in Strongly Interacting Fermions

报告人：陈静远

时间：9月20日（周三）16:00

单位：清华大学物理系

地点：理科楼C302报告厅

Non-Fermi liquid is a class of states of matter emerged from strongly interacting fermions, characterized by the absence of stable quasiparticle excitation, and hence drastically deviate from our Fermi gas intuition. Many studies on such systems are based on phenomenological propositions; concrete theoretical results are extremely rare and any of them can serve as a long-term anchor of the field. I will present that one particular response property -- the static magnetic response -- can be derived from first principles under very general assumptions. The result is formulated in terms of Berry curvature, which is a concept widely used for non-interacting fermions, but here adopted for strongly interacting fermions.

4Ultrafast Spectroscopy Characterization toward Next Generation High Performance Electronic and Optoelectronic Devices

报告人：孙栋，北京大学

时间：9月20日（周三）10:10

单位：北京大学现代光学研究所

地点：物理楼中楼211

Ultrafast science & technology is one of the most exciting fields in science and engineering today. In this talk, first I’ll introduce basic aspects about ultrafast spectroscopy and its role towards the development of next generation high performance electronic and optoelectronic devices. Then I’ll describe several representative work regarding ultrafast spectroscopy characterization of two dimensional materials and topological materials that were performed in ICQM by our group during the past few years. These work includes the following: valley polarization dynamics and exciton dynamics of transitional metal dichalcogenides MoS2; anisotropic response of black phosphorus under high electric field and high magnetic field; and photo response of three dimensional Dirac/Weyl semimetals.

5Open-closed rational conformal field theories

报告人：Liang Kong，Tsinghua University

时间：9月20日（周三）15:30

单位：中科院理论物理研究所

地点：Room 322, ITP

In this talk, I will give a review of the mathematical foundation of the boundary-bulk (or open-closed) rational conformal field theories. In particular, we will discuss all the ingredients of an open-closed conformal field theory, including bulk fields OPE, boundary fields OPE, boundary conditions, modular invariance conditions, Cardy conditions, boundary states, etc. As a consequence, we obtain a precise mathematical description of open-closed rational conformal field theories. Using this precise mathematical language, one can formulate precisely and prove rigorously the so-called "boundary-bulk duality" (or open-closed duality). If time permits, I can also briefly mention how it leads to a complete classification of gapless edges of 2+1D topological orders.

6Star Formation Across Cosmic Time

报告人：Yong Shi，Nanjing University

时间：9月21日（周四）14:00

单位：清华大学物理系

地点：蒙民伟科技南楼 S727

Stars including our Sun are born in clouds of cold gas. Understanding how gas converts into stars across cosmic time is a big challenge in modern astronomy. In the early universe, primordial gas with little or no metals collapse into early-generation stars whose radiation re-ionizes the universe. The subsequent rising of the cosmic star-formation-rate (SFR) density until z～2 follows by a rapid decline toward the current universe. The driving mechanism of this cosmic SFR evolution is related to the cold gas reservoir available within the galaxies and its capability of forming new stars. In this talk, I will review recent progresses including our own works in understanding the evolution of cosmic star formation, with the focus on answering three key questions: how does cosmic star formation start, how does cosmic star formation evolve, and how does star formation stop?

7Probing Light-Matter Interactions in Polar Semiconductor Materials

报告人：Qihua Xiong，Nanyang Technological University

时间：9月21日（周四）14:00

单位：清华大学物理系

地点：理科楼C302报告厅

The interaction of light with matter gives rises to a wide range of linear and nonlinear phenomena that we are familiar with, such as absorption and scattering, spontaneous or stimulated emission, and second harmonic generation. In polar semiconductors, the electromagnetic field of light polarizes the matter leading to the formation of elemental excitations such as excitons and exciton polaritons, due to long-range dipolar force as well as additional coupling to the optical fields.

8Dirac physics and topological photonics

报告人：蒋建华，苏州大学

时间：9月21日（周四）14:00

单位：北京大学现代光学研究所

地点：物理楼中楼211

The celebrated Dirac equation is not only the foundation of quantum field theory, but also the parent model of many later advances in physics. One of thekey notion derived from Dirac equation is the band topology for fermions in various condensed matters. Recently this notion is extended to bosonic systems, such as in photonics. I will briefly introduce the background, fundamental challenges and recent advances in the search of photonic topological materials. Band degeneracy and topology enriched by space symmetry in all dielectric photonic crystals is emphasized. Synergy with linear and quantum optics is also introduced.

9Optical response of metal nanostructures controlled by mode coupling and interference

报告人：阮智超，浙江大学

时间：9月22日（周五）14:00

单位：北京大学现代光学研究所

地点：物理楼中楼211

In this talk, we briefly review our recent efforts on the manipulation of the light scattering, absorption, and mode excitation through the mode coupling and interference. Especially, we develop a general coupled-mode theory to capture the ubiquitous nature of mode coupling and interference and give a unified picture from both the temporal and the spatial views. Based on the temporal coupled-mode theory, we will show how to design nanowire structures to realize strong absorption enhancement or substantially reduced scattering in the applications of cloak sensors, transparent electrodes and photodetector. As the examples for the spatial domain, we will discuss how to concentrate the surface plasmon polariton (SPP) excitation through the prism coupling method and how to achieve the spatial differentiator and integrator based on a simple Kretschmann prism configuration.

10Cold gas in galaxies: single-dish surveys in the

报告人：Barbara Catinella，University of Western Australia

时间：9月22日（周五）15:00

单位：清华大学物理系

地点：蒙民伟科技南楼 S727

A detailed knowledge of how gas cycles in and around galaxies, and how it depends on their structural and star formation properties, as well as environment, is crucial to understand galaxy formation and evolution. This requires sensitive surveys of cold gas for representative samples of galaxies, able to probe the gas-poor regime. I will present results based on the recently completed, extended GALEX Arecibo SDSS Survey (xGASS), which includes the deepest observations of cold gas in galaxies currently available, and will discuss results obtained via spectral stacking of the largest stellar mass-selected sample with atomic hydrogen data assembled to date. I will argue that, even in the era of the Square Kilometre Array and its precursors, there are important scientific areas where large single-dish telescopes such as Arecibo and FAST can uniquely contribute.

11走向统一的自然力（上）

报告人：厉光烈，中科院高能物理研究所

时间：9月22日（周五）16:00

单位：中科院理论物理研究所

地点：Room 322, ITP