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清华大学物理系

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2016 / . 08 / . 19

学术报告:Spin dynamics in inhomogeneously magnetized systems

2016年8月31日(周三)上午10:30,物理系seminar:

 

报告题目:Spin dynamics in inhomogeneously magnetized systems

报告人:   Teruo Ono

  Institute for Chemical Research, Kyoto University, Uji, Japan

报告时间:2016-8-31    10:30

报告地点: 理科楼三楼报告厅(C302)

报告摘要:Worldwide efforts are underway to create revolutionary and energy-efficient data storage technology such as magnetoresistive random access memory (MRAM). An understanding of spin dynamics in inhomogeneously magnetized systems is indispensable for further development of nanoscale magnetic memories. This lecture provides a transparent picture of inhomogeneously magnetized systems, such as magnetic nanowires with domain walls and disks with magnetic vortices, and presents not only technological developments and key achievements but also the unsolved puzzles and challenges that stimulate researchers in the field. 

Firstly, the basic concept of an inhomogeneously magnetized system is described by introducing a magnetic vortex structure in a magnetic disk. A magnetic domain wall in a magnetic nanowire is also provided as a typical example. The magnetic field-driven dynamics of these inhomogeneously magnetized systems are described to illustrate the uniqueness of this system.

Secondly, the electric-current-induced dynamics of magnetic vortices and domain walls are described. One can flip the core magnetization in a magnetic vortex using electrical current excitation, and move a domain wall by current injection into a wire. The next part focuses on the applications of the current-induced-magnetization dynamics in devices. The basic operations of two kinds of magnetic memories—magnetic vortex core memory and magnetic domain wall memory—are demonstrated. 

The lecture describes not only the current understanding about inhomogeneously magnetized systems, but also the unexpected features that have emerged. It concludes with prospects on future developments, in which more surprises will certainly be found.

个人简介:

Teruo Ono received the B.S., M.S., and D.Sc. from Kyoto University in 1991, 1993, and 1996, respectively.

After a one year stay as a postdoctoral associate at Kyoto University, he moved to Keio University where he became an assistant professor. In 2000, he moved to Osaka University where he became a lecturer and an associate professor. Since 2004, he has been working at Kyoto University, where he is now a professor. He has published over 280 technical articles in peer-reviewed journals, including book chapters and review articles, and has given more than 90 invited presentations at international conferences.

He served as Conference Co-Chair of the 8th International Symposium on Metallic Multilayers (MML) in 2013, and in the program committees of various international conferences on magnetism and spintronics. He is a member of the IEEE Magnetics Society and is an editor of the Japanese Journal of Applied Physics.

 

Contact Prof. Ono, Institute for Chemical Research, Kyoto University, Uji, Japan; e-mail: ono@scl.kyoto-u.ac.jp

2016 / . 08 / . 19

学术报告:Diagrammatic Monte Carlo Method for Correlated System

2016年8月19日(周五)下午3点,量子物质科学协同创新中心&物理系seminar:

 

报告题目:Diagrammatic Monte Carlo Method for Correlated System

报告人:   邓友金  教授  中国科学技术大学

报告时间:2016-8-19    15:00

报告地点: 理科楼B315

报告摘要:Diagrammatic Monte Carlo (DiagMC) method is to stochastically sample the abstract configuration space in terms of perturbative Feynman diagrammatic series. While leading to an exponential growth of computational complexity as diagram order, the fermion sign is also responsible for the convergence of the perturbative diagrammatic series for many quantum systems. DiagMC can be directly applied to the thermodynamic limit—i.e., infinite system size, and moreover, take the advantage of well-known field-theoretical techniques to run the calculation in a self-consistent mode. In this talk, I shall describe the basic formulation of DiagMC, and then discuss two applications. We study the two-dimensional fermionic Hubbard model, provide finite-temperature results and obtain the ground-state phase diagram for superfluids of different symmetries for a significant range of interaction strength and doping fraction. We also find “fingerprint” evidence of the thermal spin-ice state for the quantum Heisenberg antiferromagnet on the pyrochlore lattice—a frustrated system. 

Refs. EPL110 57001 (2015), PRX5 041041 (2016), PRL116 177203 (2016).

 

报告人简介:邓友金,男,1974年生于福建。1997年毕业于北京师范大学物理学系,2000年于北京师范大学获得理论物理专业硕士学位,2004年于荷兰Delft University of Technology获得理学博士学位。2009年以中国科学院“百人计划”教授引进到中国科学技术大学近代物理系。2010年受聘为美国麻省大学Amherst分校兼职助理教授 (Adjunct Assistant Professor)。是Phys. Rev. Lett., Phys. Rev. B, Phys. Rev. E, Phys. Lett. B, Physica A和Physica E的审稿人,也是澳大利亚研究理事会(Australian Research Council, ARC)的评审专家。邓友金教授的研究领域为统计物理、计算物理、和量子模拟。从2000年起,一直从事于高效蒙特卡洛方法的设计及其在统计物理模型的应用,探索相变和临界理论;从2008年开始涉足基于光和冷原子的量子模拟的相关理论;从2010年开始探索强关联量子多体的高效蒙特卡洛方法。自2002年以来共发表研究论文70余篇,其中61篇发表于Nature系列或Physical Review系列。

2016 / . 08 / . 15

学术报告:Publishing your research with Elsevier

2016年8月22日(周一)上午10点,量子物质科学协同创新中心&物理系seminar: 

 

报告题目:Publishing your research with Elsevier

 

报告人:   Claudia Lupp, PhD - Editor in Chief, Heliyon

 

报告时间:2016-8-22    10:00

 

报告地点: 理科楼三楼报告厅(C302)

 

 摘要:

 

Claudia has been an editor for over a decade including positions at Nature, Nature Communications and in her most recent role at Elsevier’s new open access journal Heliyon. In her seminar she will guide you through the publishing process from manuscript preparation to publication, providing you with useful information and tips on effective presentation of your research, complying with Elsevier’s publication ethics guidelines, how to manage the peer review process, and the benefits of open access. She will also introduce you to Heliyon, the scientific journal that publishes quality research across all disciplines and provides editorial excellence, fast publication, and high visibility for all published papers.

2016 / . 06 / . 23

学术报告:Theory of high temperature superconductivity of monolayer FeSe on the STO substrate and the transport theory of 2D superconductors

2016年6月27日(周一)下午3点,量子物质科学协同创新中心&低维量子物理国家重点实验室&物理系seminar:

 

报告题目:Theory of high temperature superconductivity of monolayer FeSe on the STO substrate and the transport theory of 2D superconductors

报告人:   李定平 教授     北京大学物理系

报告时间:2016-6-27    15:00

报告地点: 理科楼三楼报告厅(C302)

报告摘要:Part one: Pairing in one atomic layer thick two dimensional electron gas by a single at band of high energy longitudinal optical phonons is considered. The polar dielectric SrTiO3 (STO) exhibits such an energetic phonon mode and the 2DEG is created both when one unit cell FeSe layer is grown on its (100) surface and on the interface with another dielectric like LaAlO3 (LAO). We obtain a quantitative description of both systems by solving the gap equation for Tc for arbitrary Fermi energy, electron-phonon coupling and the phonon frequency, and direct (RPA) electron-electron repulsion strength. The high temperature superconductivity in 1UCFeSe/STO is possible due to a combination of three factors: high LO phonon frequency, large electron-phonon coupling and huge dielectric constant of the substrate suppression the Coulomb repulsion.

Part two: We use Ginzburg-Landau theory to study the transport of 2D superconductors. Based on improved Gaussian variational approximation, we calculate the transition temperature and superfluid density. Using time dependent Ginzburg Landau theory, we obtain the IV curve and magneto resistance. Then We  compare the theoretical results with the experimental data.

 Bio: 工作领域:高温超导理论,特别是二类超导体涡旋物态物理性质的研究;波色爱因斯坦凝聚理论;多体量子理论和场论方法的研究;量子霍尔效应。

 

        科研成果:李定平教授近年来对高温超导体涡旋态和BEC相关领域进行了系统研究,已发表SCI收录论文数篇,其中包括Reviews of Modern Physics 1篇,Physical Review Letters 4篇, Physical Review B 14篇,Physical Review A 4篇, Nuclear Physics B 4篇,Physics Letters B 2篇.

2016 / . 06 / . 23

学术报告:Theory of high temperature superconductivity of monolayer FeSe on the STO substrate and the transport theory of 2D superconductors

2016年6月27日(周一)下午3点,量子物质科学协同创新中心&低维量子物理国家重点实验室&物理系seminar:

 

报告题目:Theory of high temperature superconductivity of monolayer FeSe on the STO substrate and the transport theory of 2D superconductors

报告人:   李定平 教授     北京大学物理系

报告时间:2016-6-27    15:00

报告地点: 理科楼三楼报告厅(C302)

报告摘要:Part one: Pairing in one atomic layer thick two dimensional electron gas by a single at band of high energy longitudinal optical phonons is considered. The polar dielectric SrTiO3 (STO) exhibits such an energetic phonon mode and the 2DEG is created both when one unit cell FeSe layer is grown on its (100) surface and on the interface with another dielectric like LaAlO3 (LAO). We obtain a quantitative description of both systems by solving the gap equation for Tc for arbitrary Fermi energy, electron-phonon coupling and the phonon frequency, and direct (RPA) electron-electron repulsion strength. The high temperature superconductivity in 1UCFeSe/STO is possible due to a combination of three factors: high LO phonon frequency, large electron-phonon coupling and huge dielectric constant of the substrate suppression the Coulomb repulsion.

Part two: We use Ginzburg-Landau theory to study the transport of 2D superconductors. Based on improved Gaussian variational approximation, we calculate the transition temperature and superfluid density. Using time dependent Ginzburg Landau theory, we obtain the IV curve and magneto resistance. Then We  compare the theoretical results with the experimental data.

 Bio: 工作领域:高温超导理论,特别是二类超导体涡旋物态物理性质的研究;波色爱因斯坦凝聚理论;多体量子理论和场论方法的研究;量子霍尔效应。

 

        科研成果:李定平教授近年来对高温超导体涡旋态和BEC相关领域进行了系统研究,已发表SCI收录论文数篇,其中包括Reviews of Modern Physics 1篇,Physical Review Letters 4篇, Physical Review B 14篇,Physical Review A 4篇, Nuclear Physics B 4篇,Physics Letters B 2篇.

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