量子热力学、拓扑绝缘体、光电器件、超导体、引力波 | 本周直播物理讲座
1 Path Integral Approach to Quantum Thermodynamics | 量子物质系列报告
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Path Integral Approach to Quantum Thermodynamics
7月15日（周三） 下午15:00-16:00
主讲人 | 全海涛 （北京大学）
腾讯会议ID：353 873 611（限300人）
会议密码：0715
直播链接：https://meeting.tencent.com/l/EBUtNzp6PZ9K（人数不限）
Work belongs to the most basic notions in thermodynamics but it is not well understood in quantum systems, especially in open quantum systems. By introducing a novel concept of work functional along individual Feynman path, we invent a new approach to study thermodynamics in the quantum regime. Using the work functional, we derive a path-integral expression for the work statistics. By performing the expansion, we analytically prove the quantum-classical correspondence of the work statistics. In addition, we obtain the quantum correction to the classical fluctuating work. We can also apply this approach to an open quantum system in the strong coupling regime described by the quantum Brownian motion model.This approach provides an effective way to calculate the work in open quantum systems by utilizing various path integral techniques. As an example, we calculate the work statistics for a dragged harmonic oscillator in both isolated and open quantum systems.
组织者：王磊、万源
主办：中科院物理所理论室、学术服务部
协办：《物理学报》、CPL、CPB、《物理》四刊
2Quantum Transport Phenomena in Magnetic Topological Insulators | 先进量子技术系列讲座
报告人：王亚愚，清华大学）
时间：7月16日（周四）15:00-16:00
单位：中科院物理所
参加方式：讲座以线上形式进行，采用“腾讯会议”软件
会议ID：642 167 165
会议密码：0716
直播链接：https://meeting.tencent.com/l/QI9kcMVe2LMs
摘要：
A remarkable breakthrough in the field of topological quantum matter is the discovery of topological insulator (TI) with nontrivial bulk band topology and metallic boundary states. The TIs are expected to host a rich variety of novel quantum transport phenomena, especially when the time reversal symmetry is broken. In particular, the quantum anomalous Hall effect (QAHE), namely the quantum Hall effect in zero magnetic field, may occur in two-dimensional ferromagnetic TIs without Landau levels. In order to realize this effect, the system must fulfill the stringent requirements of being topological, ferromagnetic, and insulating simultaneously. In this talk, we will first give a brief introduction about TI and the QAHE. Then we will show how to fine tune the electronic and magnetic properties in Cr doped (Bi,Se)2Te3 topological insulator thin films grown by molecular beam epitaxy, which eventually led to the observation of QAHE. In the end, we will present more recent developments in this field, including the axion insulator phase and helical Chern insulator phase in the newly discovered MnBi2Te4 antiferromagnetic TI.
报告人简介：
Yayu Wang received his B.S. degree in physics from the University of Science and Technology of China in 1998 and his Ph.D. from Princeton University in 2004. From 2004 and 2007 he was a Miller research fellow at UC Berkeley. After a brief visit to MIT, he joined the physics department of Tsinghua University in December 2007. His recent research interests include transport studies of topological insulators and STM studies of high temperature superconductors.
报告直播二维码
主 题：仿生学对光电器件设计的启示
主讲人：范智勇 教授
主讲人介绍
内容简介
报告人：Dr. Zixiang Li，University of California, Berkeley / Lawrence Berkeley National Laboratory
时间：7月16日（周四）10:00
单位：中科院物理所
系列报告采用腾讯会议室+网络直播的形式
Online Meeting Room ID (Tencent Meeting): 602 888 600
Password: 0716
Live link：https://meeting.tencent.com/l/oN5t0A0TR9LM
Unified understanding of high-Tc superconductors, including both copper-oxide and iron-based materials, remains one of the most important challenges in modern condensed matter physics. It has been highly desired that unbiased theoretical and numerical approaches with no uncontrolled approximation can be developed to address key issues such as pairing mechanism and the nature of pseudogap in high-Tc superconductors. In this talk, I will discuss our recent progresses in understanding pairing mechanism, pseudogap, and non-Fermi-liquid behaviors in unconventional superconductors, utilizing approximation-free quantum Monte-Carlo calculations and other analytical approaches. I will first discuss our recent quantum Monte Carlo and field-theory studies on unconventional superconductivity and non-Fermi liquid behavior emergent from doped valence bond solid phase, which shares many important properties with superconductivity in doped resonating valence bond (RVB). Then I will present our theoretical calculations about exotic superconducting fluctuations in overdoped cuprate, regarding recent ARPES experiments. In the third part, I will discuss pairing mechanism of high-Tc superconductivity in single-layer FeSe/STO material. Lastly, I will discuss potential future directions in this research field.
Brief CV of Dr. Zi-Xiang Li:
Dr. Zi-Xiang Li got his Ph.D degree from Institute for Advanced Study, Tsinghua University in 2017 under the supervision of Prof. Hong Yao. Currently, Dr. Zi-Xiang Li works as a Gordon and Betty Moore Postdoctoral fellow at University of California, Berkeley and Lawrence Berkeley National Laboratory in Prof. Dung-Hai Lee’s group. Dr. Zi-Xiang Li’s research interest lies is exploring strongly correlated systems and topological matters. Recently, he focuses on quantum phase transition and critical point, unconventional superconductors, interaction effects and Majorana zero mode in topological phases and sign problem in quantum Monte-Carlo simulation.
5Pseudo-Gauge Field and Piezo-electromagnetic Response in Topological Materials
报告人：Prof. Chao-Xing Liu，PSU
时间：7月15日（周三）9:30
单位：Kavli Institute for Theoretical Sciences，UCAS
参会方式： Zoom
Online Meeting Room (zoom.com): https://zoom.com.cn/j/98821416246
Meeting ID: 988 2141 6246
In topological materials with Dirac equation as low energy effective theory, the strain can normally play the role of pseudo-gauge field. In this talk, we will show this pseudo-gauge field can give rise to topological piezo-electromagnetic response. In particular, we will discuss two examples. First, we consider a Dirac type of topological phase transition in a 2D crystal and find that the piezo-electric coefficient will exhibit a discontinuous change across the phase transition due to the change of local Berry curvature. Second, we consider the axion charge density wave phase in the 3D time reversal invariant Weyl semimetals and show that the dynamical strain can induce a topological dynamical piezo-magnetic response.
报告人：Ligong Bian (边立功)，Chongqing University
时间：7月14日（周二）15:00
单位：中科院高能所
参会方式： Zoom
ID：2151583083
Domain walls (Cosmic strings) can form after the spontaneous symmetry breaking of discrete symmetry (U(1) symmetry). In this talk, I will first briefly review the current and future GW detectors sensitivity to the SGWB from decay of these topological defects, and then discuss the possibility to search for BSM physics with the stochastic gravitational wave background (SGWB) from decay of topological defects produced after the first-order phase transition.
报告人：Prof. Ning Chen（陈宁），Nankai University
时间：7月16日（周四）15:00
单位：中科院高能所
参会方式： Zoom
ID：2151583083
In this talk, we discuss the possible domain wall solutions in new physics beyond the Standard Model. The domain wall is one type of the topological defects, which can appear when there is degenerate vacua associated with the spontaneous symmetry breaking. Their existences are problematic in cosmology. I will show that they can arise in the two-Higgs-doublet model (2HDM) with the spontaneous CPV vacuum. In such a scenario, one automatically needs explicit CPV parameters in the 2HDM potential to collapse the domain wall. Generally speaking, such domain wall collapse can lead to gravitational waves, and we briefly mention how are they related to the energy scale of the new physics. By combining the constraints from the big bang nucleosynthesis and the latest EDM measurements, we show how are the very tiny explicit CPV parameters in the 2HDM constrained.
更多报告信息：中国物理学会期刊网学术讲座列表