腐蝕電化學原理概述及其在海洋腐蝕研究中的應用 | 本周物理學術講座
報告人：董俊華，中科院金屬研究所
時間：1月12日（週五）10:00
單位：中科院物理所
地點：M樓253會議室
實施國家海洋戰略，建設海洋強國，離不開發展海洋裝備；建設海洋工程，更離不開海洋工程材料的支撐；海洋工程和海洋工程材料是拓展海洋空間、開發海洋資源的物質前提。
報告人：徐軍，北京大學電子顯微鏡實驗室
時間：1月9日（週二）14:00
單位：北京大學現代光學研究所
地點：物理樓 中211
電子/離子雙束系統在微納尺度上成像、分析及加工方面一直扮演著重要的角色。本講座將介紹掃描電鏡和聚焦離子束的基本原理及其應用。將和同學們探討在儀器使用中基本參數的選擇及其影響等。
報告人：Xingjiang Zhu，Monash University ARC Centre of Excellence for Gravitational Wave Discovery
時間：1月10日（週三）10:00
單位：中科院理論物理研究所
地點：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.
報告人：Jean-Philippe Ansermet，洛桑聯邦理工學院
時間：1月10日（週三）14:00
單位：北京師範大學物理系
地點：物理樓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
報告人：Mauricio Jorquera，IAS, Princeton
時間：1月10日（週三）15:30
單位：中科院理論物理研究所
地點：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.
報告人：E. Ma，Johns Hopkins University
時間：1月11日（週四）9:30
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.
報告人：Xin (Sunny) Wang，City University of Hong Kong
時間：1月11日（週四）10:00
單位：中科院物理所
地點：M236會議室
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.
報告人：Antonios Tsokaros
時間：1月11日（週四）16:00
單位：北京大學科維理天文與天體物理研究中心
地點：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.
報告人：LAW, Kam Tuen, Hong Kong University of Science and Technology
時間：1月11日（週四）16:00
單位：清華大學物理系
地點：鄭裕彤講堂
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.
報告人：Mingpu Qin, College of William & Mary
地點：理科樓C302報告廳
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.
報告人：尉東光，卡爾蔡司美國公司離子顯微技術研發中心
最近幾年，以氣相場離子源（GFIS）為基礎的高亮度（>109 A/cm2.sr），小束斑（<0.5nm）的氦/氖離子束技術得到了長足的發展，並在微納加工領域得到重要應用，特別是在亞10納米尺度上的表徵及加工能力上表現出其它離子束技術無法相比的優越性，使其在納米材料及納米器件的加工及表徵領域引起廣泛重視。
本報告將簡要介紹氣相場離子源技術的原理和氦/氖離子束的產生機制、特徵及相關儀器，
報告人：Ran He，IFW Dresden
地點：D-210報告廳
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.
報告人：張金星，北京師範大學
時間：1月12日（週五）15:00
單位：中科院物理所
地點：D樓210會議室
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 5 d 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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