腐蚀电化学原理概述及其在海洋腐蚀研究中的应用 | 本周物理学术本周五在中科院物理所M楼253会议室

1腐蚀电化学原理概述及其在海洋腐蚀研究中的应用

报告人：董俊华，中科院金属研究所

时间：1月12日（周五）10:00

单位：中科院物理所

地点：M楼253会议室

实施国家海洋战略，建设海洋强国，离不开发展海洋装备；建设海洋工程，更离不开海洋工程材料的支撑；海洋工程和海洋工程材料是拓展海洋空间、开发海洋资源的物质前提。然而，由于海洋环境的复杂性及其严酷的腐蚀性，基础设施和重要工业设施在海洋环境中的电化学腐蚀问题十分严重，是影响服役安全、寿命、可靠性的最重要因素。腐蚀电化学原理和方法是认识和处理各种海洋腐蚀问题的重要基础和手段。

2扫描电镜/聚焦离子束原理及应用简介

报告人：徐军，北京大学电子显微镜实验室

时间：1月9日（周二）14:00

单位：北京大学现代光学研究所

地点：物理楼中211

电子/离子双束系统在微纳尺度上成像、分析及加工方面一直扮演着重要的角色。本讲座将介绍扫描电镜和聚焦离子束的基本原理及其应用。将和同学们探讨在仪器使用中基本参数的选择及其影响等。

3太极计划数据分析系列报告之六：Inferring the population properties of binary neutron stars with gravitational-wave measurements of spin

报告人：Xingjiang Zhu，Monash University ARC Centre of Excellence for Gravitational Wave Discovery

时间：1月10日（周三）10:00

单位：中科院理论物理研究所

地点：ITP New Building 6420

The recent LIGO-Virgo detection of gravitational waves from a binary neutron star merger event GW170817 and discoveries of its accompanying electromagnetic signals marked a new era for multi-messenger astronomy. In the coming years, advanced gravitational-wave detectors are likely to detect tens to hundreds of similar events. Neutron stars in binaries can possess significant spin, which is imprinted on the gravitational waveform via the effective spin parameter. We develop a fiducial model, informed by radio observations, in order to predict the effective spin of merging binaries like GW170817. We explore the astrophysical inferences made possible by gravitational-wave measurements of spin.

4Heat-Driven Spin Torques In Magnetic Metals, Insulators And Antiferromagnets

报告人：Jean-Philippe Ansermet，洛桑联邦理工学院

时间：1月10日（周三）14:00

单位：北京师范大学物理系

地点：物理楼106

Heat-driven spin torques in spin valves were characterized by quasi-static transport measurements and electrically-detected magnetic resonance. They can be understood with an extension of the two-current model that includes an entropy current. Heat-driven spin torques in insulators were observed by magnetic resonance (Phys.Rev.B 2017). They can be accounted for by a modified Landau-Lufshitz equation derived from a variational principle. We predict heat-driven spin torque in antiferromagnets and a narrowing of the antiferromagnetic resonance in selected materials. This opens up the possibility of THz spin torque oscillators

5All-Order Volume Conjecture for Closed 3-Manifolds from Complex Chern-Simons Theory

报告人：Mauricio Jorquera，IAS, Princeton

时间：1月10日（周三）15:30

单位：中科院理论物理研究所

地点：Room322

I"ll review some general aspects of complex Chern-Simons theory on hyperbolic 3-manifolds, focusing on the case of gauge group G=SL(2,C). After a brief introduction to the Volume Conjecture (VC), for knot complements and, a very recent mathematical proposal, for closed hyperbolic 3-manifolds, I"ll show how complex Chern-Simons theory is related with them and how this connection leads to a novel generalization of the most recently proposed VC for closed 3-manifolds.

6Controlling nucleation in amorphous-to-crystal transition to break the speed limit of phase-change memory

报告人：E. Ma，Johns Hopkins University

时间：1月11日（周四）9:30

单位：中科院物理所

地点：M楼253会议室

This talk describes an example of advancing materials performance from the nanoscale, the theme of research at CAMP-Nano. We report a success story (F. Rao et al., Science 2017) that take advantage of metastable alloys for nanoelectronics, setting an unprecedented operation speed for memory and switch applications. Specifically, we have designed a new phase-change alloy with drastically reduced crystal nucleation stochasticity to accomplish sub-nanosecond switching for cache-type phase-change random-access memory (PCRAM) technology.

7Composite pulses for robust control of spin qubits

报告人：Xin (Sunny) Wang，City University of Hong Kong

时间：1月11日（周四）10:00

单位：中科院物理所

地点：M236会议室

Spin qubits in semiconductor quantum dots are promising candidates for quantum information processing due to their demonstrated long coherence time, reasonably high control fidelity, and prospects for scalability. Despite these successes, there remain great challenges to overcome, with the major one being decoherence, the process through which the qubit loses the information it carries while interacting with its environment. Various techniques are proposed to combat decoherence, including the dynamically corrected gates using composite pulse sequences that are able to cancel both nuclear and charge noises simultaneously while performing a quantum gate operation. In this talk, I will present recent developments on these noise-compensating composite pulses for spin qubits, including gate sequences which are simultaneously resilient to nuclear and charge noises at both single- and two-qubit level. I will also present our attempt to improve the control fidelity of capacitively coupled spin qubits by making simple modifications to control sequences that are already used in the laboratory. With time permitting, I will discuss the possibility to achieve the same level of robustness using analytically designed smooth pulse instead of the square pulse traditionally used. These results mark an important step forward in using semiconductor spin qubits as the platform for scalable, fault-tolerant quantum computation.

8The initial value problem of general relativity and applications in astrophysics

报告人：Antonios Tsokaros

时间：1月11日（周四）16:00

单位：北京大学科维理天文与天体物理研究中心

地点：KIAA-PKU Auditorium

Classical general relativity is usually referred as one of the most beautiful physical theories and one reason for this claim is that it admits an elegant geometrically inspired initial value formulation, with deep connections to physical reality. After tracing the main ideas that led to the current view of understanding, I will present the main formulations that lead to astrophysically important solutions both in vacuum as well as in the presence of matter. The numerical implementation of these methods will be presented in the context of the Compact Object CALculator (COCAL) code whose purpose is to solve for any general-relativistic system in equilibrium or quasi-equilibrium. This includes rotating stars, binary neutron stars, binary black holes, black hole-toroids and many others. Future prospects will be discussed.

9Ising superconductivity, Majorana fermions and spin valley Hall effect in transition metal dichalcogenides

报告人：LAW, Kam Tuen, Hong Kong University of Science and Technology

时间：1月11日（周四）16:00

单位：清华大学物理系

地点：郑裕彤讲堂

Ising superconductors with in-plane upper critical fields several times higher than the Pauli limits have been discovered in transition metal dichacogenides such as MoS2 and NbSe2 thin films. These Ising superconductors have very strong Ising spin-orbit couplings (SOC), in the order of 10 to 100meV, which pin electron spins to the out-of-plane directions. This is in contrast to Rashba SOC which pins electron spins to in-plane directions. Here, we explain how Ising SOC can enhance the in-plane upper critical field of Ising superconductors and be used to create Majorana fermions [4]. We will also discuss a spin-triplet nodal superconducting phase in gated MoS2. At the end of the talk, I will discuss a new mechanism of valley Hall effect induced by Ising and Rashba SOC. We call this effect spin valley Hall effect.

10Stripe phase in 2D Hubbard model

报告人：Mingpu Qin, College of William & Mary

时间：1月12日（周五）10:00

单位：清华大学物理系

地点：理科楼C302报告厅

Recent experiments show spin and charge order and their fluctuation might be the key to understand high- temperature superconductivity. In this talk, I will show our recent work on the stripe phase in the 2D Hubbard model at 1/8 doping with numerical methods. I will first give a brief introduction of the auxiliary field Quantum Monte Carlo (AFQMC) method and the minus sign problem. Then I will discuss the constrained path Monte Carlo (CPMC) method which was designed to attack the minus sign problem. I will present our recent development, i.e., the self-consistent CPMC method. With this method we establish the existence of stripe phase in the ground state of 1/8 doped Hubbard model. I will conclude by addressing the remaining problems in the study of doped 2D Hubbard model.

11氦/氖离子束纳米加工方法：原理、仪器及应用

报告人：尉东光，卡尔蔡司美国公司离子显微技术研发中心

时间：1月12日（周五）10:00

单位：中科院物理所

地点：M楼253会议室

最近几年，以气相场离子源（GFIS）为基础的高亮度（>109 A/cm2.sr），小束斑（<0.5nm）的氦/氖离子束技术得到了长足的发展，并在微纳加工领域得到重要应用，特别是在亚10纳米尺度上的表征及加工能力上表现出其它离子束技术无法相比的优越性，使其在纳米材料及纳米器件的加工及表征领域引起广泛重视。

本报告将简要介绍气相场离子源技术的原理和氦/氖离子束的产生机制、特征及相关仪器，并对目前氦/氖离子束技术在微纳加工领域的重要应用成果做较为详细的介绍。其中着重介绍在亚10纳米尺度下材料和器件的直接加工技术，基于氦/氖离子束的离子束曝光技术，氦/氖离子束对材料的辐照损伤，非导电、磁性及生物等材料的高分辨率成像表征，以及通过离子束辐照/注入对材料/器件的结构和性能进行改性等新的应用方向和领域。本报告将为感兴趣的研究人员了解这项新兴的纳米加工技术提供基本原理机制和典型应用实例，以期在纳米前沿领域研究中得到重要应用。

12Realizing High Power Factor and High Figure-of-Merit in Half-Heusler Compounds

报告人：Ran He，IFW Dresden

时间：1月12日（周五）10:00

单位：中科院物理所

地点：D-210报告厅

Heat can be converted into electricity through the thermoelectric (TE) effect. For an ideal TE device, the conversion efficiency is governed by the figure-of-merit (ZT); meanwhile the output power density is related to the power factor (PF) of the TE materials. In the application for waste-heat recovery, high PF is considered equally important as high ZT. However, most of the reported high ZTs were realized in TE materials with extremely low thermal conductivity, yet a combination of high ZT and high PF are much less reported. In this talk, I will present the enhancement of ZT in the half-Heusler based compounds through boosting the PF. The mechanisms of the enhancement such as improving the band degeneracy, tuning the carrier scattering mechanism, and nanostructuring, etc. are discussed in detail. Based on the optimized compositions, a high heat-to-power conversion efficiency of ~9%, as well as a record-high output power density of 22 W cm-2 were realized. These work mark the half-Heusler based compounds promising candidate for thermoelectric applications.

13Spin physics in complex oxide heterostructures

报告人：张金星，北京师范大学

时间：1月12日（周五）15:00

单位：中科院物理所

地点：D楼210会议室

The exotic properties in strongly correlated electronic materials such as high-TC superconductivity in cuprates, colossal magnetoresistance in manganites, magnetoelectric coupling in multiferroics are intimately related to the coexistence and competition of nearly degenerate states — charge, lattice, orbital, and spin. This provides a strong motivation to explore materials or structures in which the spin degree of freedom can be manipulated using new strategies, e.g. an electrical knob, apart from traditional magnetic field. In this talk, after a short introduction of my oxide group in Beijing Normal University, I shall share some of our recent insights about spin physics in complex oxide thin films and heterostructures, covering 3d, 4d and 5d transition metal perovskite oxides. Majorly using scanning probe techniques (where local magnetism can be characterized with a spatial resolution), I would like to introduce how to design emerging correlated behaviors using epitaxial growth with an atomic precision and then control magnetism under external stimuli, which may provide a wide platform for potential next-generation spintronic devices.

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