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光谱椭偏学:原理、仪器及在纳米测量中的应用 | 本周物理学术讲座

1光谱椭偏学:原理、仪器及在纳米测量中的应用

报告人:刘世元,华中科技大学

时长:10月20日(周五)10:00

单位:中科院物理研究所

地点:M楼236

椭偏仪是一种利用光的偏振态改变信息来分析样品的重要科学仪器,广泛应用于材料光学常数、薄膜厚度等参数的测量表征。其中,穆勒矩阵椭偏仪代表了椭偏仪的最高水平,可以测得一个4乘4阶的穆勒矩阵共16个参数,因而可以获得更为丰富的测量信息。本报告首先介绍传统椭偏测量的基本原理及在多层光学薄膜表征中的应用;然后阐述IC集成电路、OLED/OPV、柔性电子等领域中普遍采用的超薄层状纳米结构及其测量挑战;接下来介绍本课题组的若干最新进展,包括自主研制的国内第一台高精度宽光谱穆勒矩阵椭偏仪,及其在IC纳米结构形貌测量、二维材料单原子层膜厚表征、OLED/OPV材料分子取向各向异性分析、原子层沉积(ALD)薄膜成核过程原位测量、以及卷对卷(roll-to-roll)大面积纳米结构薄膜量产在线监测中的应用;最后展望椭偏测量的应用前景及未来发展趋势。

2Amonalous Metals and Failed Superconductors

报告人:Steven Kivelson,美国科学院院士,斯坦福大学

时长:10月18日(周三)10:00

单位:清华大学物理系

地点:理科楼 C302 报告厅

Prof. Kivelson has made many seminal contributions to condensed matter physics. He is a pioneer in many fundamental concepts and models in correlated electron systems. Examples include fractional topological charges, electron nematic/sematic states, spin-liquid phases, and so on. His publications have been cited more than 30000 times and his H-index is 87.Prof. Kivelson was elected as Fellow of the American Academy of Arts and Sciences in 2001 and as Member of National Academy of Sciences in 2010. He was awarded John Bardeen Prize in 2012. Moreover, he has mentored dozens of PhD students and postdocs who have been very successful in their fields of research.

3Artificial graphenes : Dirac matter beyond condensed matter

报告人:Gilles Montambaux,Laboratoire de Physique des Solides

时长:10月19日(周四)11:00

单位:清华大学物理系

地点:Lecture Hall C302, New Science Building

These cones, which describe the band structure in the vicinity of the two connected energy bands, are characterized by a topological “charge”. They can be moved in reciprocal space by appropriate modification of external parameters (pressure, twist, sliding, stress, etc.). They can be manipulated, created or suppressed under the condition that the total topological charge be conserved. The merging between two Dirac cones is thus a topological transition that may be described by two distinct universality classes, according to whether the two cones have opposite or like topological charges. We have recently found a system in which the two classes may be observed.In this presentation, I will discuss several aspects of the scenarios of merging or emergence of Dirac points as well as the experimental investigations of these scenarios in condensed matter and beyond.

4迈向量子隐形传输薛定谔的细菌

报告人:尹璋琦,清华大学交叉信息研究院量子信息中心

时长:10月19日(周四)14:00

在薛定谔猫理想实验中把生与死制备到了量子叠加态,揭示了量子力学的推论与宏观世界的经验不同寻常的矛盾,引发了无数的研究。我们提出把细菌冷冻起来放到电力学振子的表面,通过把振子制备到量子叠加态上,实现微生物的量子叠加态。我们的工作基于最近实验上的一系列突破,使得我们可以把直径15微米,厚度100纳米的薄膜机械振子通过微波腔边带冷却的办法冷到量子基态附近,然后制备机械振子与微波腔模的量子纠缠态等非经典态。细菌的质量远比振子有效质量小,因此放置了细菌的振子其频率与品质因子不会有显著变化。应可被冷却到量子基态,并制备到量子叠加态。我们还研究了在这个系统中用类似磁共振力显微镜的办法测量细菌中生物大分子的缺陷和自由电子的位置,然后制备出生命体内部的电子自旋与其质心位置之间的量子纠缠态。我们最后讨论了如何用这个系统实现微生物内部自旋态之间的量子隐形传态。

5超高真空-四探针扫描隧道显微镜系统的彻底改造及其在石墨烯输运研究中的应用

报告人:马瑞松,N04 group, IOP

时长:10月19日(周四)15:00

扫描隧道显微镜(STM)发明于二十世纪八十年代初,这一强大的工具赋予人们研究和操控微观体系的能力。传统的单探针STM可以用来研究样品的形貌和材料局域的电子结构等性质,然而其无法测量低维体系的横向电输运特性。为了将输运测试能力与极高空间分辨率相结合,人们陆续开发了双探针、三探针甚至四探针等多探针STM系统。其中,四探针STM同时兼容标准的四端输运测试方式,可以更准确地对样品输运性质进行原位表征。本次报告主要介绍了对一台商用超高真空四探针扫描隧道显微镜在减振与阻尼、扫描结构、导热链接与热屏、针尖定位SEM的替换、分时复控电路单元等诸多方面的升级改造过程,从而更好地实现四探针系统在石墨烯等二维材料形貌表征与输运性质研究中的有效应用。

6Berry phase of Bloch electrons and materials properties

报告人:冯济, Peking University

时长:10月19日(周四)16:00

单位:清华大学物理系

地点:理科楼郑裕彤讲堂

Berry phase and associated physical effects have attracted broad attention in recent years, particularly in condensed matter physics. In this colloquium, I will begin with an exposition of the concept of Berry phase in Bloch electrons in extended solids, highlighting various materials properties derivable from Berry phase and with an emphasis on the computational aspects. Subsequently, a few examples will be discussed to demonstrate materials prediction and discovery centering on the notion of Berry phase, including valleytronics materials, quantum anomalous Hall effect and particularly our recent progress on the theory of impurity states in semiconductors.

7Electromagnetic counterparts of gravitational wave sources

报告人:Bing Zhang,University of Nevada

地点:蒙民伟科技南楼 S727

I will discuss the theoretical models of various electromagnetic (EM) counterparts of gravitational wave (GW) sources due to NS-NS, NS-BH, and BH-BH mergers, which include a short gamma-ray burst and afterglow, a kilonova/mergernova and afterglow, a plausible long-duration X-ray event, and a speculative fast radio burst. Finally, I will report the observational data of the first GW event with the detections of EM counterparts and the theoretical implications from these observations.

8拓扑物理学的发展:蜂窝结构带来的启示

报告人:胡晓,筑波大学

时长:10月20日(周五)14:00

单位:中科院半导体研究所

地点:5号楼LED会议室

Honeycomb lattice plays an extremely important role in fostering topology physics as known from the Haldane model and the Kane-Mele model [1]. Recently, we propose a way to achieve all-dielectric topological photonics starting from honeycomb structure. We identify a pseudospin degree of freedom in electromagnetic (EM) modes hosted by honeycomb lattice, which can be explored for establishing topological EM states with time-reversal symmetry [2]. We demonstrate theoretically the nontrivial topology by showing photonic band inversions, and counter-propagating edge EM waves. I will show recent experimental results of microwaves which confirm our theory. The idea can also be applied for other bosonic systems such as phonons as well as electronic systems. Recent progresses and perspectives of the present approach will be discussed.

9ALP miracle: a simple unification of inflation and dark matter

报告人:殷文,IHEP

时长:10月20日(周五)16:00

单位:中科院理论物理研究所

地点:Room 6420

We propose a scenario where both inflation and dark matter are described by a single axion-like particle (ALP) in a unified manner. In a class of the minimal axion hilltop inflation, the effective masses at the maximum and minimum of the potential have equal magnitude but opposite sign, so that the ALP inflaton is light both during inflation and in the true vacuum. After inflation, most of the ALPs decay and evaporate into plasma through a coupling to photons, and the remaining ones become dark matter. We find that the observed CMB and matter power spectrum as well as the dark matter abundance point to an ALP of mass mϕ=(0.01−0.1) eV and the axion-photon coupling gϕγγ=(10^−11) GeV^−1, which are within reach of future solar axion helioscope experiments IAXO, TASTE and laser-based stimulated photon-photon collider experiments: ALP miracle. This region is hinted by several anomalies. The thermalized ALP particles contribute to hot dark matter and its abundance is given in terms of the effective number of extra neutrino species, ΔNeff≃0.03, which can be tested by the future CMB and BAO observations. We also discuss possible extensions of the ALP miracle scenario by introducing other interactions of the axion-like particle to the standard model fields.

10Metal-Catalyzed Cross-Coupling Reactions of Alkyl Electrophiles

报告人:Gregory C. Fu,美国国家科学院院士,加州理工学院

时长:10月20日(周五)16:00

单位:中科院理化研究所

地点:1号楼407

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光谱椭偏学:原理、仪器及在纳米测量中的应用 | 本周物理学术讲座

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