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清华大学物理系

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 ... 阅读全文

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

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清华大学物理系

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:... 阅读全文

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。

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清华大学物理系

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... 阅读全文

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.

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清华大学物理系

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... 阅读全文

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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清华大学物理系

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... 阅读全文

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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清华大学物理系

学术报告:The Nuclear Structure Function from BONuS

2016年6月22日下午2点半,清华核物理系列报告第38期 SerialSeminarsonNuclearPhysics(38th) 题目: TheNuclearStructureFunctionfromBONuS 报告人: Dr.JiXieZhang (UniversityofVirginia,PhysicsDepartment) ... 阅读全文

2016年6月22日下午2点半,清华核物理系列报告第38期

Serial Seminars on Nuclear Physics (38th)

 

题目:   The Nuclear Structure Function from BONuS

 

报告人: Dr. JiXie Zhang

 (University of Virginia, Physics Department)

 

时间: 2016年6月 22日 (周三) 14:30

地点:  理科楼 D203

 

摘要 Much less is known about neutron structure than that of the proton due to the absence of free neutron target.  The Barely Off-shell Nucleon Structure (BONuS) experiment at Jefferson Lab measured the inelastic electron-deuteron scattering, tagging spectator protons in coincidence with the scattered electrons. This method reduces nuclear binding uncertainties significantly and has allowed for the first time a (nearly) model-independent extraction of the neutron structure function F2n at large Bjoken-x in both the deep inelastic region and the resonance region.  The result for the neutron structure function will be presented. An outlook for the same measurement at 11 GeV beam energy and in an extended kinematic range will also be discussed.

 

 

报告人简介:张机械,博士,目前在 Univesity of Virginia 从事高能核物理研究工作。他于2001年毕业于清华大学工程物理系,2005年获得美国老领地大学物理学硕士, 2010年获得核物理博士学位。2010-2013  在Jefferson Lab 做博士后工作。2013年加入 UVA至今,主要从事电子散射相关的高能核物理研究。

 

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清华大学物理系

学术报告:Symmetry Energy of Neutron-Rich Matter and its Astrophysical Impacts

2016年6月16日(周四)下午4点,物理系colloquium: 报告题目:Symmetry Energy of Neutron-Rich Matter and its Astrophysical Impacts 报告人:Bao-An Li(Department of Physics and Astronomy, Texas A&M Unive... 阅读全文

2016年6月16日(周四)下午4点,物理系colloquium:

 

报告题目:Symmetry Energy of Neutron-Rich Matter and its Astrophysical Impacts

报告人:Bao-An Li (Department of Physics and Astronomy, Texas A&M University-Commerce)

时间:2016-6-16  16:00

地点:理科楼郑裕彤大讲堂

 

摘要:

To pin down the Equation of State (EOS) of neutron-rich nucleonic matter and understand its transport properties has long been a major science driver for both nuclear physics and astrophysics. Nuclear symmetry energy encoding the energy cost of converting protons into neutrons in nuclear medium has been the most uncertain part of the EOS of neutron-rich nucleonic matter. The magnitude and density dependence of nuclear symmetry energy determine the radii and cooling rates of neutron stars as well as the strain amplitude and frequencies of gravitational waves from spiraling neutron star binaries. Nuclear reactions in terrestrial laboratories, especially those induced by highly neutron-rich radioactive beams, provide a unique means to probe experimentally the symmetry energy of neutron-rich matter. In this talk, I will discuss the main issues concerning the density dependence of nuclear symmetry energy, its astrophysical impacts and examples of current efforts to constrain it experimentally.

 

个人简介:Dr. Bao-An Li is a Regents Professor of Physics at Texas A&M University-Commerce and a Fellow of the American Physical Society. Dr. Li received his Ph.D in physics from Michigan State University in 1991. He held research, faculty and administrative positions at Oak Ridge National Laboratory in the U.S., Niels Bohr Institute in Denmark, Hahn-Meitner Institute in Germany, Texas A&M University and Arkansas State University before becoming the Head of the Department of Physics and Astronomy at Texas A&M University-Commerce in 2006. His research interest is in understanding the dynamics of heavy-ion reactions from low to relativistic energies as well as the Equation of State of neutron-rich nucleonic matter and its astrophysical applications.  Dr. Li has published over 200 refereed and 75 non-refereed papers receiving over 13,000 citations with a H-index of 57 according to Google Scholars. He has been the Principle Investigator of CUSTIPEN (China-U.S. Theory Institute of Physics with Exotic Nuclei) funded by the U.S. Department of Energy since 2013, a member of the Executive Board of the FRIB (Facility for Rare Isotope Beams) Theory Alliance in the U.S. and the Task Force of FRIB-China Collaboration.

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清华大学物理系

学术报告:Ac engineering of spin transfer torques in magnetic tunneling junctions

2016年6月8日(周三)上午10点,量子物质科学协同创新中心&物理系seminar: 报告题目:Ac engineering of spin transfer torques in magnetic tunneling junctions 报告人: 陈晓彬 McGill University 报告时间:2016-6... 阅读全文

2016年6月8日(周三)上午10点,量子物质科学协同创新中心&物理系seminar:

 

报告题目:Ac engineering of spin transfer torques in magnetic tunneling junctions

报告人:   陈晓彬

                 McGill University

报告时间:2016-6-8    10:00

报告地点: 理科楼三楼报告厅(C302)

 

摘要:Phenomena of spin transfer torques (STTs) have been attracting persistent interests due to promising prospects of STTs in designing nano devices. By using nonequilibrium Green's function method, we derive time-averaged formulism for spin transfer torques in a noncollinear magnetic tunneling system under ac modulation within wide-band-limit approximation. Using these formulas, we further investigate ac spin transfer torques in a carbon-nanotube-based magnetic tunneling system. It shows that under ac modulation, the low-bias linear (quadratic) dependence of the in-plane (out-of-plane) torque on bias still holds, and the regular angular dependence on noncollinear angle is maintained. By introducing photon-assisted tunneling, the bias-induced components of the in-plane and out-of-plane torques can be enhanced by about 10 and 80 times, respectively. Further analysis shows that optimized enhancement can be achieved by using ac driving frequency w=e0/k, k=1,2,..., where e0 marks a remote dc transmission peak, and using ac amplitude D such that D/w maximizes a kth-order Bessel function of the first kind. Out findings suggest that ac modulation is a promising way for electrical manipulation of spin transfer torques, paving the road towards emerging nanoelectronic and spintronic devices utilizing spin transfer torques.

 

个人简介:Dr. Chen works on theoretical Physics as a postdoctoral fellow in the department of Physics at McGill University, Canada. She received her Ph.D. of condensed matter Physics from Tsinghua University in 2014 and has been conducting her postdoctoral research with Prof. Hong Guo at McGill University since then. Her early research interests were nanoscale heat transport and thermoelectricity. More recently, she has worked on the spin Caloritronics, spin thermoelectrics, valley transport, and time-dependent physics in nanostructures.

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清华大学物理系

学术报告:全光纤量子光源及其在量子信息中的应用

2016年6月7日(周二)上午10:00,量子物质科学协同创新中心&物理系seminar: 报告题目:全光纤量子光源及其在量子信息中的应用 报告人: 李小英 天津大学精密仪器与光电子工程学院 报告时间:2016-6-7 10:00 报告地点: 理科楼C109 报告摘要:小型化、低成本、易于操作和维护的量子态光源是量子信息技... 阅读全文

2016年6月7日(周二)上午10:00,量子物质科学协同创新中心&物理系seminar:

 

报告题目:全光纤量子光源及其在量子信息中的应用

报告人:   李小英

  天津大学精密仪器与光电子工程学院

报告时间:2016-6-7    10:00

报告地点: 理科楼C109

报告摘要:小型化、低成本、易于操作和维护的量子态光源是量子信息技术实用化的关键环节之一。本报告将介绍采用全光纤实验装置,以光纤锁模激光器作为泵浦源,通过光纤中的四波混频产生通讯波段光子对、频谱可控的光子对、高效率纯态单光子和高质量脉冲压缩态等超快量子态光场,及其在精密测量和量子通讯中应用的实验进展。

 

简历:李小英,天津大学精密仪器与光电子工程学院教授,博士生导师。1989年于天津大学精密仪器工程系获工学学士学位,1998年于天津大学获光学工程专业工学硕士学位,2002 年于山西大学光电研究所获光学专业理学博士学位。2002 年1月至2005 年6 月,在美国西北大学电子系做博士后,2009年3月至7月在美国西北大学电子系做高级访问学者,2005年7月至今在天津大学工作。主要从事的量子光学、非线性光学和光电信息方面的研究与教学工作。多年来致力于研制基于光学参量过程的实用化光量子器件,并探索其应用。2009年获第六届中国青年女科学家奖;2014年获王大珩光学奖中青年科技奖。

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清华大学物理系

学术报告:Interface-controlled materials for solar energy conversion: semiconducting nanocrystal-solids

2016年6月7日(周二)上午10:00,量子物质科学协同创新中心&物理系seminar: 报告题目:Interface-controlled materials for solar energy conversion: semiconducting nanocrystal-solids 报告人: Prof. Stefan Martin Wipp... 阅读全文

2016年6月7日(周二)上午10:00,量子物质科学协同创新中心&物理系seminar:

 

报告题目:Interface-controlled materials for solar energy conversion: semiconducting nanocrystal-solids

报告人:   Prof. Stefan Martin Wippermann

    Max-Planck Institute for Iron Research, Germany

报告时间:2016-6-7    10:00

报告地点: 理科楼三楼报告厅(C302)

报告摘要:Recent experimental advances demonstrate the synthesis of Colloidal nanocrystals (NCs), their arrangement in superlattices and subsequent embedding in a host matrix completely by inexpensive chemical solution processing. However, experimental techniques to probe such nanointerfaces at the microscopic level are largely unavailable. In this talk we discuss strategies how to model such NC-composites from first principles, identify relevant structural motifs and processes by atomistic thermodynamics, their impact on the resulting composite's properties and validation by experiment. We highlight approaches towards efficient solar energy conversion, such as multi-exciton generation (MEG), where a single high energy photon creates several electron-hole pairs. Focusing on Si-based nanostructures, "exotic" Si allotropes, and III-V compounds we discuss ideas to tailor the properties of NC-composites towards such novel photovoltaic architectures. 

 

个人简介:Professor Stefan Martin Wippermann got Ph.D at Paderborn University on atomic wire arrays with quasi one-dimensional electronic properties. He is now a group leader at Max-Planck Institute for Iron Research, Duesseldorf, Germany in Interface Chemistry and Surface Engineering department, electrochemical solid-liquid interfaces. His research interests are energy materials, surface chemistry in nanostructures, electron transport, theoretical vibrational and excitation, et. al.

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清华大学物理系

学术报告:Dark Photons at LHCb

2016年6月8日(周三)下午3点,物理系seminar: 报告题目:Dark Photons at LHCb 报告人:薛巍 Center for Theoretical Physics, MIT 报告时间:2016-6-8 15:00 报告地点:理科楼三楼报告厅(C302) 摘要:Dark photon... 阅读全文

2016年6月8日(周三)下午3点,物理系seminar:

 

报告题目:Dark Photons at LHCb

报告人:薛巍    

              Center for Theoretical Physics, MIT

报告时间:2016-6-8  15:00

报告地点:理科楼三楼报告厅(C302)

摘要:Dark photons appear in many well-motivated dark matter scenarios,  

which leads to a worldwide effort to search for them. In this talk,  I will present two 

novel search methods for dark photons at the LHCb experiment. One is an exclusive 

search in charm meson decay, and the other is a fully data-driven inclusive search

based on di-muon resonances. These searches advance particle physics by showing

how LHCb can have sensitivity to large regions of unexplored dark-photon parameter

space.

 

报告人简历:

2001-2005: Bachelor of Engineering,Department of Civil Engineering, University of Shanghai for Science and Technology

2005-2008:Master of Theoretical Physics,Department of Physics,

Peking University 

2009-2012:PhD of  High-Energy Physics, Cosmology,Department of 

Physics, McGill University

2012-2014:Postdoc at INFN/SISSA

2014-now:  Postdoc at Center for Theoretical Physics, MIT

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清华大学物理系

学术报告:Atomic Imaging Functional Heterostructures and Interfaces by Phasing Coherent Bragg Rods for Correlated Materials and Energy Systems

2016年5月30日(周一)下午3点,量子物质科学协同创新中心&物理系seminar: Topic: Atomic Imaging Functional Heterostructures and Interfaces by Phasing Coherent Bragg Rods for Correlated Materials and Energy S... 阅读全文

2016年5月30日(周一)下午3点,量子物质科学协同创新中心&物理系seminar:

Topic: Atomic Imaging Functional Heterostructures and Interfaces by Phasing Coherent Bragg Rods for Correlated Materials and Energy Systems

Speaker: Dr. Hua Zhou

                 Advanced Photon Source, Argonne National Laboratory, Department of Energy, USA

Time: 15:00 PM, Monday, May 30th, 2016 

Location: Lecture Hall B315, New Science Building (理科楼 B315)

Abstract: Ubiquitous in a wide range of nature processes and technologies, a subtle modification (e.g. structurally, chemically, or electronically) near an interface can have a decisive effect on properties of the collective as well as each individual. A compelling case manifesting such subtlety is oxide heterostructures and heterointerfaces exhibiting fascinating emergent behaviors due to numerous combinative contributions of atomic structures and chemistries, which can be effectively harnessed for the design of advanced materials for information and energy applications and accelerating materials integration into advanced devices. Surface/interface X-ray scattering from modern synchrotron sources integrated with phase retrieval direct methods provides a very powerful toolkit to decipher the interfacial subtlety. This is essential to our ability to provide a quantitative and realistic description of the interfacial boundaries by which to engineer properties of oxide interfaces using atomic structure-driven design principles in a reliable and controlled manner. In this seminar, I will firstly give a brief introduction of how to obtain atomic mapping of oxide heterostructure and heterointerfaces with sub-Ångstrom resolution by phase retrieving coherent Bragg rods, wherein complete atomically structural information hidden, in particular on the COBRA method in combination with the difference map algorithm achieving unprecedented speed of convergence and precision. In the following, I will demonstrate a few recent studies in the exploration of oxide heterostructures and heterointerfaces for information and energy applications by applying the direct method, such as revealing structural motifs responsible for 2DEG and superconductivity adjacent with heterointerfaces, catching structural perturbations in response to varied polar energy landscapes, differentiating at the atomic-layer level the complicated cation distribution relevant with creating new polar order and enhancing oxygen reduction activities, and depth-resolved mapping oxygen-octahedral connectivity patterns essential with incipient functionalities of heterostructures. In the end, I will give a short commentary on future opportunities in X-ray studies of oxide interfaces and heterostructures enabled by the exciting advancements towards ultimate storage rings, in particular with enhanced high-energy and coherence capabilities.

 

简历:周华博士在美国能源部阿贡国家实验室中的先进光子源大科学装置担任研究物理学家。从20119月开始他负责管理先进光子源中由可调制扭摆器构架的束线实验站。同时他还负责开发和拓展专门针对先进材料制备,功能测试和应用方向的原位,操作同步和实时X射线研究。科研课题特别集中在研究复杂环境中表面与界面现象和过程方面 (例如,外延纳米结构和异质结构的薄膜沉积,强关联凝聚态体系中的新兴物理现象,各种电化学能源存储和转化中的界面问题)。他在应用X射线相复原直接法表征和揭示外延薄膜的表面/界面结构变化与动力学方面极富经验。 加入先进光子源部之前他分别在美国能源部布鲁克海文国家实验室的国家同步辐射光子源部和阿贡国家实验室的化学科学与工程部从事博士后的研究工作。他与2007年年底在美国佛蒙特大学获得材料科学博士学位。他在薄膜/异质结构和表面/界面X射线技术方面发表了一系列书章,综述和60多篇同行评议的论文。很多相关论文发表在国际重要影响力和知名杂志上,包括Nature, Nature Physics, PNAS, Energy and Environmental Science, Advanced Materials, Advanced Functional Materials, Nano Letters, and ACS-Nano 等。他还在各种国际会议,大学和国家实验室做过20多次的邀请报告或专题讲座。

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清华大学物理系

学术报告:Laser Spectroscopy and Electron Imaging of Metal-Hydrocarbon Radicals

2016年5月23日(周一)上午10:30,量子物质科学协同创新中心&物理系seminar: 报告题目:Laser Spectroscopy and Electron Imaging of Metal-Hydrocarbon Radicals 报告人: Prof. Dong-Sheng Yang Department of Chemistr... 阅读全文

2016年5月23日(周一)上午10:30,量子物质科学协同创新中心&物理系seminar:

 

报告题目:Laser Spectroscopy and Electron Imaging of Metal-Hydrocarbon Radicals

报告人:   Prof.  Dong-Sheng Yang

Department of Chemistry, University of Kentucky, USA

报告时间:2016-5-23    10:30

报告地点:理科楼三楼报告厅(C302)

报告摘要:

 

Hydrocarbons are not only the major constituents of oil and natural gas, but also the most abundant, low-cost stock for functionalized organic chemicals. Because of their chemical inertness, the transformation of the hydrocarbons to value-added products requires the activation of thermodynamically stable C-H and C-C bonds. Metal-mediated bond activation circumvents this problem by stimulating inert hydrocarbons to react with other molecules. Metal-Hydrocarbon radicals formed in the entrance channel and subsequent steps are transient and reactive and play essential roles in such activation reactions. In our work, metal-hydrocarbon reactions are carried out in a pulsed supersonic molecular beam source; reaction intermediates and products are identified by time-of-flight mass spectrometry and investigated by pulsed-field-ionization zero-electron-kinetic-energy, mass-analyzed threshold ionization, IR-UV photoionization, and electron velocity-map imaging spectroscopies. In this talk, we will discuss metal-hydrocarbon radicals formed by metal adsorption on aromatic surfaces and by metal-mediated dehydrogenation, C-C bond breakage and coupling, and cyclo-oligomerization of small alkenes and alkynes. The discussion will include the bonding and structures, electronic states and energies, and formation mechanisms of the radicals.

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清华大学物理系

学术报告:层状材料原子尺度生长机理的特性与共性及其物性调控

2016年5月19日(周四)下午4点,量子物质科学协同创新中心&物理系colloquium: 报告题目:层状材料原子尺度生长机理的特性与共性及其物性调控 报告人:张振宇 (中国科学技术大学) 时间:2016-5-19 16:00 地点:理科楼郑裕彤大讲堂 摘要:石墨烯、硅稀、二硫化钼、拓扑绝缘体、h-氮化硼、黑磷。。。近年来凝聚... 阅读全文

2016年5月19日(周四)下午4点,量子物质科学协同创新中心&物理系colloquium:

 

报告题目:层状材料原子尺度生长机理的特性与共性及其物性调控 

报告人:张振宇 (中国科学技术大学)

时间:2016-5-19  16:00

地点:理科楼郑裕彤大讲堂

摘要:石墨烯、硅稀、二硫化钼、拓扑绝缘体、h-氮化硼、黑磷。。。近年来凝聚态物理与材料科学的发展以层状结构这一大家族的一个个新成员的发现为一大导向。一方面,每一个新成员都有其鲜明的个性,不同成员之间的结合更显特色;另一方面,整个大家族又有其共性,比如单层材料与衬底之间、层与层之间几乎都是以弱的范德瓦耳斯力耦合到一起。对每一个成员的深层理解,都可能对真正走进这一大家族有普适性价值。这里我们从量子力学的第一性原理计算出发,辅以多尺度理论模拟,揭示石墨烯在金属衬底上从成核到晶元级大面积生长过程中所可能依赖的原子级动力学过程与微观机制。基于这些研究,我们提出可在低温下生长出高质量大面积单晶石墨烯的动力学通道,并结合实验验证这些预言。进一步,我们从单层石墨烯扩展到双层石墨烯,从石墨烯扩展到其它层状材料及其异质结,揭示其生长过程中的特性与共性。最新的研究亮点包括预言可外延生长单层蓝磷的理想衬底与新颖机制,以及如何精确调控大幅度提高在磁性拓扑绝缘体中实现量子反常霍尔效应的温度。这方面的研究不仅可丰富我们在非平衡状态下低微材料生长领域的知识积累,同时也对调控这类材料的功能性质与器件应用有指导意义。

 

个人简介:张振宇,中国科学技术大学教授。1982年毕业于武汉大学并经CUSPEA项目赴美留学,1989年获美国罗格斯大学博士学位。1989-1993年在美国加州大学圣巴巴拉分校从事博士后研究。1993-1995年在美国威斯康星大学麦迪逊分校任职,1995-2010年在美国橡树岭国家实验室任职,并于1997-2011年在美国田纳西大学任教。回国前长期与中科院物理所等国内单位合作研究,2008年初开始将合作重心转向中国科大, 并于2011年初全职回科大。长期从事凝聚态理论计算和模拟研究工作, 采用多重尺度方法探讨低维体系与纳米材料的形成机理与物性; 近期的研究重心是清洁能源功能材料的量子设计,以及其它新型量子材料的理论预测与实验验证。 

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清华大学物理系

学术报告:Anomalous phonon transport/heat diffusion in nano scale systems

2016年5月13日(周五)下午4点,量子物质科学协同创新中心&物理系seminar: 报告题目:Anomalous phonon transport/heat diffusion in nano scale systems 报告人:Prof. Baowen Li (University of Colorado, Boulder) 时间:2... 阅读全文

2016年5月13日(周五)下午4点,量子物质科学协同创新中心&物理系seminar:

 

报告题目:Anomalous phonon transport/heat diffusion in nano scale systems

报告人:Prof. Baowen Li     (University of Colorado, Boulder)

时间:2016-5-13  16:00

地点:理科楼三楼报告厅C302

报告摘要:Both experimental and numerical works in recent years have shown that thermal conductivity due to phonons in low dimensional nano scale systems like nanotube, nanowire, polymer chain, graphene, and other 2D materials are size dependent. In this talk, I will present a general theoretical understanding of the anomalous thermal conductivity. More specifically, I will discuss how the anomalous thermal transport (a macroscopic phenomenon) is connected with the anomalous heat diffusion (a microscopic process).

References:

1. C W Chang et al, Phys Rev. Lett 101, 075903 (2008).

2. X-F Xu et al, Nat Comm 10, 1038 (2014).

3. S Liu et al, Phys Rev. Lett 112, 040601 (2014).

个人简介:

 

Dr. Li received B. S from Nanjing University, M. Sci from Institute of Acoustics, the Chinese Academy of Science, and Ph. D from Oldenburg University, Germany in 1985, 1989 and 1992, respectively. He joined National University of Singapore (NUS) as assistant professor in 2000, and become full professor in 2007 and worked there until 2014. He has been 2014/2015 Russell Severance Springer Professor at Department of Mechanical Engineering, UC Berkeley. In August 2015, he joined Department Mechanical Engineering, University of Colorado, Boulder as the Rennie Family Endowed Professor.

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清华大学物理系

学术报告:Optoelectronics of Graphene-based Van der Waals Heterostructures

2016年5月13日(周五)上午10:00,量子物质科学协同创新中心&物理系seminar: 报告题目:Optoelectronics of Graphene-based Van der Waals Heterostructures 报告人:Qiong Ma MIT 时间:2016-5-13 10:00 地点:理科楼三楼报告厅C3... 阅读全文

2016年5月13日(周五)上午10:00,量子物质科学协同创新中心&物理系seminar:

 

报告题目:Optoelectronics of Graphene-based Van der Waals Heterostructures

报告人:Qiong Ma   MIT  

时间:2016-5-13  10:00

地点:理科楼三楼报告厅C302

报告摘要:The photoresponse of materials is governed by energy relaxation pathways of photo-excited electron-hole pairs. In graphene, due to frequent electron-electron collision and weak electron-lattice coupling, a novel transport regime is reached in which the photo-generated carrier population can remain hot while the lattice stays cool. In this talk, I will show that light is converted to electrical currents through a hot-carrier assisted thermoelectric effect in intrinsic graphene[1]. The thermal energy slowly leaks to the lattice via two distinct processes of electron-phonon coupling that can be tuned by temperature and charge density[2]. We also implemented a scheme to control the initial stage of photo-excited carriers before they collide with ambient carriers (less than ten femtoseconds) to form a hot Fermi-Dirac distribution, which is realized in a graphene-boron nitride-graphene heterostructure[3]. 

      The weak electron-phonon coupling and frequent electron-electron scattering revealed above strongly alter the nature of particle and energy transport, leading to a collision dominant fluid behavior for electrons. In the last part of the talk, I will discuss our observation of highly-ordered photocurrent patterns at the charge neutral point of graphene, which is likely related to the ballistic thermal transport of hot electron-hole plasma in the hydrodynamic regime[4]. 

 

[1] N. Gabor, J. Song, Q. Ma, N. Nair, T. Taychatanapat, K. Watanabe, T. Taniguchi, L. Levitov    and P. Jarillo-Herrero, Science 334, 648 (2011).

[2] Q. Ma, N. Gabor, T. Andersen, N. Nair, K. Watanabe, T. Taniguchi and P. Jarillo-Herrero, Phys. Rev. Lett. 112, 247401 (2014).

[3] Q. Ma, T. Andersen, N. Nair, N. Gabor, M. Massicotte, C. Lui, A. Young, W. Fang, J. Kong, K. Watanabe, T. Taniguchi, N. Gedik, F. Koppens and P. Jarillo-Herrero, Nature Physics (2016) doi:10.1038/nphys3620.

 

[4] Q. Ma, et al., “Geometric Edge Photocurrent Generation and Hydrodynamics in Graphene.”    In preparation (2016)

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清华大学物理系

学术报告:新材料及新性能的大设计探讨

2016年4月28日(周四)上午10:30,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:新材料及新性能的大设计探讨 报告人:王晓临 澳大利亚伍伦贡 (卧龙岗)大学 时间:2016-4-28 10:30 地点:理科楼C109 报告摘要:当前,我们正处于充满挑战和竞争... 阅读全文

2016年4月28日(周四)上午10:30,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:新材料及新性能的大设计探讨

报告人:王晓临  

               澳大利亚伍伦贡 (卧龙岗)大学

时间:2016-4-28  10:30

地点:理科楼C109

报告摘要:当前,我们正处于充满挑战和竞争时代。如何才能发现更多新材料、新特性,和新器件,这是代表全球科学研究和战略发展的趋势。本报告在总结新材料和新特性的发展前沿的基础上, 提出和讨论一些设计和研究新材料的新观点和正在尝试的新方法,以期获得新型功能材料及新的功能特性,期望对于如何设计新型电子材料,自旋电子材料,多电功能材料,或设计新型电子,自旋,光学等特性,以及对材料基因组等研究有所借鉴。

本报告也总结我们在高压诱导大幅度增加铁基超导电流及机制,Rashba BiTeCl 体系中的费米面拓扑转变的结果,silicene, 热电,及多铁材料研究的一些重要结果。 并着重讨论自旋零带半导体的新的进展,并将提出它们的一些新的物理概念及其在下一代自旋电子学中的应用。也会共同探讨一下三个材料和性能探索的终极问题。物质、材料及性能越来越复杂,还应该有更多新材料、新物质及新物质粒子、新奇异性能等存在并等待被探索。它们还有多少?它们是什么?如何找到它们?

个人简介:王晓临,澳大利亚Wollongong大学,超导与电子材料研究所教授与副所长,自旋与电子材料研究组组长,澳大利亚物理学院 Fellow,澳大利亚国家教授级未来学者。

 

山东大学物理本科及固体物理硕士,2000年在澳大利亚Wollongong大学获材料科学博士学位。曾先后在奥地利、日本、美国著名大学研究机构从事研究工作。研究领域广泛,涵盖新型功能材料的设计及其试验和理论研究、涉及超导材料、自旋电子材料、磁性铁电材料、热电材料等。尤其在新材料设计方面,在国际上首次独创提出了自旋零带半导体 (Spin gapless Semiconductors) 新型材料,已在国际上被试验和理论验证。在国际著名杂志上发表论文超过300篇,很多重要工作发表国际顶级杂志,如:Nature Materials, Science Advances,  Physical Review Letters, Advanced Materials, Advanced Functional Materials等。论文引用近6000 多次。曾获得英女王伊丽莎白二世学者称号、美国材料学会和国际超导技术中心奖,和 WOLLONGONG大学校长合作奖。近年来以项目带头人身份承担了十多项澳大利亚基金项目,项目经费超过1000万澳元。现为澳大利亚物理学院 Fellow, 澳大利亚国家教授级未来学者。

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清华大学物理系

学术报告:Building scalable quantum networks based on solid state qubits

2016年4月28日(周四)上午10:30,量子物质科学协同创新中心&物理系seminar: 报告题目:Building scalable quantum networks based on solid state qubits 报告人:杨森 (斯图加特大学) 时间:2016-4-28 10:30 地点:理科楼三楼报告厅 C302 ... 阅读全文

2016年4月28日(周四)上午10:30,量子物质科学协同创新中心&物理系seminar:

 

报告题目:Building scalable quantum networks based on solid state qubits

报告人:杨森  (斯图加特大学)

时间:2016-4-28  10:30

地点:理科楼三楼报告厅 C302

报告摘要:Because of their great potential as the most secure communication system and their promising scalability in quantum computing, quantum information networks emerged and have been an important field in physics research in recent 15 years. Building practical quantum network calls for long coherence time and feasibly scale-up physical systems. In recent 10 years, point defects with individual controllable spins come into the focus due to their scalability, ability of interacting with photons, and long coherence times. One most promising system is the nitrogen vacancy centers in diamond. In this talk, we will start by introducing the multi-qubit quantum register composed of an electron spin and several nuclear spins around, the ways to operate them and their coherence properties. By designing photonic structures, we increase the photon collection efficiency which leads to ways of high fidelity spin readout. Emission based and absorption based quantum optical interfaces are realized based on these techniques.  We will discuss how to build scalable quantum networks from these two approaches. In the end, progress in other solid state qubit systems like vacancies in SiC, rare earth ion dopant in YAG crystal will be discussed. 

 

个人简介:杨森毕业于清华大学物理系基础科学班,在加州大学圣迭戈分校从事关于半导体量子阱里激子的量子现象的研究,于2009年获得物理博士学位。目前在德国斯图加特大学第三物理研究所从事基于固体点缺陷的量子光学的研究。

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清华大学物理系

学术报告:单层FeSe/SrTiO3界面超导的超快动力学研究

2016年4月19日(周二)上午10:00,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&物理系系列学术讲座: 题目:单层FeSe/SrTiO3界面超导的超快动力学研究 报告人:赵继民 研究员 中国科学院物理研究所 报告时间:2016-4-19 10:00 报告地点:理科楼三楼报告厅(C302) ... 阅读全文

2016年4月19日(周二)上午10:00,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&物理系系列学术讲座:          

 

题目:单层FeSe/SrTiO3界面超导的超快动力学研究

报告人:赵继民  研究员

              中国科学院物理研究所

报告时间:2016-4-19   10:00

报告地点:理科楼三楼报告厅(C302)

报告摘要:Since the discovery of single-layer FeSe/SrTiO3 interface high-Tc superconductivity by Professor Xue and his colleagues, various investigations have been carried out to elucidate its superconductivity mechanism. Here we demonstrate the evidence of superconductivity from ultrafast optical spectroscopy, using weak detection of the quasiparticle ultrafast dynamics. We obtain that Tc = 68 (-5/+2) K and Δ(0) = 20.2 ± 1.5 meV. Especially, from the quasiparticle lifetime, we directly obtain the e-phonon coupling constant λ = 0.48, which is three times of that in bulk FeSe.  We further find a 0.05 THz coherent acoustic phonon branch in the capping layer, which provides an additional decay channel to the gluing bosons.

 

报告人简介:赵继民,中国科学院物理研究所研究员,博士生导师,表面物理国家重点实验室。他于1995年和1998年在清华大学物理系分布获得学士和硕士学位,于2004年在密西根大学(安娜堡)物理系获得博士学位,经过博士后研究工作,于2007年回国到中科院物理所工作。他的研究兴趣主要是量子材料的超快动力学与相干光谱,研究超导体、拓扑量子态、二维材料等与光的相互作用,重点关注激发态的超快动力学和多自由度元激发的相干调控。

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