报告介绍 Abstract： When atomically thin two-dimensional materials are layered, they often form incommensurate noncrystalline structures that exhibit long-period moire patterns when examined by scanning probes. In this talk I present a methodology that uses information obtained from ab initio calculations performed on short-period crystalline structures to derive effective Hamiltonians that are able to effic...

报告介绍 Biosketch：　　Professor Qian Niu obtained a B.S. from Peking University in 1981. He went to the University of Washington for graduate studies, and received his Ph.D. in physics in 1985. Now he is a Trull Centennial Professor of Physics at the University of Texas at Austin, and an Adjunct Chair Professor at the International Center for Quantum Materials in Peking University. He has worked on the the...

报告介绍 Abstract： Spin is the fundamental electronic quantum degrees of freedom in solid state materials. In superconductors, Cooper pairs, as composed of two spin-1/2 particles, can have spin-1 angular momentum, leading to spin-triplet pairings. In this talk, we show that Majorana zero modes in solids has universal pure spin-triplet correlations for both time-reversal broken and respect topological superc...

报告介绍 报告摘要： 晶体管是现代历史中最重要的发明之一，是所有现代电器的关键主动元件。它的出现引发了现代社会的信息技术革命，对全球经济发展和人类进步产生了不可估量的影响。对于场效应晶体管来说，影响其性能的因素有很多，申请人将其归为三个方面：一方面是组成晶体管器件的材料，即半导体、金属和栅介质；另外一个方面是利用这些材料组成器件时，各个材料之间所形成的界面，即半导体/金属、栅介质/半导体和半导体/衬底之间的界面；...

报告介绍 Abstract： Low power is desirable for battery-powered electronics, such as mobile phone and internet of things (IOTs) devices etc. Spintronics is considered as an emerging technology that can offer this property based on its data non-volatility/fast operation/easy integration with CMOS. And spin transfer torque random access memory (STT-MRAM) has attracted much attention from academics and industrie...

报告介绍 Abstract： The maximum solar-to-electric power conversion efficiency of a conventional solar cell is determined by the Shockley-Queisser limit of ~33% [1]. In this lecture, I will discuss efforts in my group over the past a few years to explore photophysical mechanisms that may be used to exceed this limit [2]. The first approach is to create two electron-hole pairs from the absorption of one photon...

报告介绍 Abstract： The ability to directly probe ultrafast phenomena on the nanoscale is essential to our understanding of excitation dynamics on surfaces and in nanomaterials. Recently, a new ultrafast STM technique that couples terahertz (THz) pulses to the scanning probe tip of an STM was demonstrated (THz-STM), providing simultaneous 0.5 ps time resolution and 2 nm spatial resolution under ambient labor...

报告介绍 Abstract： The feverish research activity on lead halide perovskites has been fueled by their exceptional optoelectronic properties, e.g., in solar cells and light-emitting devices. Hybrid lead halide perovskites exhibit carrier properties that resemble those of pristine nonpolar semiconductors despite static and dynamic disorder, but how carriers are protected from efficient scattering with charged...

报告介绍 报告摘要： 随着同步辐射光源和自由电子激光的发展，x射线量子光学得到越来越多的关注，报告里提出了一种储存x射线脉冲的方法，这为以后的量子通信和量子计算提供了一种新的选择。References:Xiangjin Kong, WenTe Liao and Adriana Pálffy. Field control of single x-ray photons in nuclear forward scattering. New J. Phys. 16, 013049(2014).Xiangjin Kong and Adriana Pálffy. Stopping Narrow-Band X-Ray Puls...

报告介绍 报告摘要： 电子在磁场中由于受到洛仑兹力而产生霍尔效应，然而声子作为电中性的准粒子却不能与磁场相互作用，所以在2005年当声子霍尔效应在顺磁材料中被实验发现时，人们很惊讶，其后续的理论解释也一直存在争议。我们得到声子霍尔效应在弹道输运量子器件中的存在,提出了声子霍尔效应热导率的拓扑表述, 并发现了声子霍尔效应中的拓扑相变现象 最近，通过半经典的波包动力学方，我们得到各种热霍尔效应的利用贝利曲率表达的通用霍尔...

报告介绍 Abstract： “What is the value of scientific research? Everybody knows that in our days more than ever before a man or a woman who wishes to make a genuine contribution to the advancement of science has to specialize, … Being engaged in such a specialized activity one naturally at times stops to think what it is good for. Has the promotion of knowledge within a narrow domain any value in...

报告介绍 报告摘要： Electronic transport of charge and spin can be controlled by external electric and magnetic fields. One of the most remarkable transport phenomena at mesoscale and nanoscale is the universal conductance fluctuation. Due to the quantum interference, the amplitude of such fluctuation stays constant independent of the average conductance and sample details. Based on a variety of nanomaterial...

报告介绍 Abstract： 　　Electrochemical scanning tunnelling microscopy (EC-STM) is a powerful tool which gives the opportunity to investigate surfaces and its adsorbates with unprecedented resolution under in-situ electrochemical conditions. During EC-STM experiment, the tunnelling current between the tip and the substrate is measured. Due to its working principle, EC-STM can’t image insulator. However...

报告介绍 报告摘要： 　　石墨烯是一种由单层碳原子构成的具有六角蜂窝结构的二维材料，它的很多新奇电学性质是由其晶格结构决定的。过去几年，我们一直致力于通过晶格对称性破缺来调控石墨烯的能带结构和电学性质。在本报告中我将介绍晶格对称性破缺在石墨烯中引入的几种新奇量子物态，包括缺陷引入的磁性、转角引入的non-Abelian规范势和新奇手征费米子、AB-BA畴界中的拓扑边界态等。报告人简介：　　何林2009年7月于北京大学物理学院获得博...

报告介绍 Abstract：Carbon monoxide, CO, serves as the most important tracer to map molecular abundance in the universe. Furthermore, CO is involved in many physical, chemical and biological processes on Earth.  In order to observe and study processes involving CO in the laboratory, sensitive and quantitative experimental detection schemes for nascent CO are of obvious importance and much effort has ther...

报告介绍 Abstract： Inorganic nanoparticles (NPs) have the ability to self-organize into variety of extended and terminal structures and so do many molecular and nanoscale compounds given sufficient number of translational and rotational degrees of freedom. Analysis of experimental data for all NPs (metal, semiconductor, ceramic..) indicate a general trend of self-assembly under a much wider range of co...