半导体低维结构中的量子相 | 本周物理学讲座

来源：中国物理学会期刊网

1半导体低维结构中的量子相

报告人：常凯，中科院半导体研究所超晶格国家重点实验室

时间：12月26日（周四）16:00

单位：清华大学

地点：理科楼郑裕彤讲堂

半导体低维结构不仅具有重要的应用价值，同时也是探索形形色色演生规范场及其相关量子效应的绝佳实验平台，它可以把维度、关联效应和能带拓扑性质结合起来，研究由于这些效应相互影响导致的新量子相。在本次报告中，我们将结合我们的工作讨论在近年来在半导体低维结构中呈现出的演生规范场及其诱导的量子相。

2Reduced quantum anomaly in a quasi-two-dimensional Fermi superfluid

报告人：刘夏姬，澳大利亚Swinburne University of Technology

时间：12月24日（周二）10:00

单位：北京师范大学

地点：科技楼C区602

A two-dimensional (2D) harmonically trapped interacting Fermi gas is anticipated to exhibit a quantum anomaly and possesses a breathing mode at frequencies different from a classical scale invariant value. The predicted maximum quantum anomaly (~10%) has not been confirmed in experiments. Here, we theoretically investigate the zero-temperature density equation of state and the breathing mode frequency of an interacting Fermi superfluid at the dimensional crossover from three to two dimensions. We find that the simple model of a 2D Fermi gas with a single s-wave scattering length is not adequate to describe the experiments in the 2D limit, as commonly believed. A more complete description of quasi-2D leads to a much weaker quantum anomaly, consistent with the experimental observations. We clarify that the reduced quantum anomaly is due to the significant confinement-induced effective range of interactions, which is overlooked in previous theoretical and experimental studies.

3Driven dissipative crystals of matter and light: phase transitions, symmetries and transient dynamics

报告人：李相良，ETH Zurich (苏黎世联邦理工)

时间：12月24日（周二）10:00

单位：清华大学

地点：物理系理科楼B315

This talk focuses on self-organised crystalline phases experimentally realized in a system with a BEC dispersively coupled to a high-finesse optical cavity and transversally illuminated by a pump laser beam. Self-organization phase is interesting from a condensed matter viewpoint as it features a cavity-mediated long-range atom-atom interaction and allows real-time access to the system dynamics via the leakage of the cavity photon field. This system thus provides an ideal platform for studying the universalities of phase transitions such as symmetry breaking and critical behaviours. I will first introduce the generation of the self-organised crystal via a superradiant phase transition and its general properties. I will then talk about our recent experiment on a first order structural phase transition between two different self-organised crystalline phases. we study the transition in real time using quantum optical methods and observe a transient dynamics of the system after the phase transition. This goes beyond equilibrium thermodynamics.

4超短激光脉冲与原子分子相互作用

报告人：何峰，上海交通大学

时间：12月25日（周三）15:10

单位：北京大学

地点：物理楼西楼202教室

2018 年诺贝尔物理奖的一半奖金授予了Mourou 和Strickland，以表彰他们发明的啁啾脉冲放大技术。这一技术使激光强度提升6个数量级，并直接打开了超快激光物理研究的大门，使得人们在飞秒（10-15 秒）甚至阿秒（10-18 秒）时间尺度观测原子分子的超快动力学过程成为可能，为拍摄单分子电影、控制化学键的合成和断裂、理解微观世界的物理规律奠定了基础。在本报告中，我利用数值模拟含时薛定谔方程的方法，研究氢气分子在超短强激光脉冲作用下的解离过程，揭示分子内电子-电子、电子-原子核在飞秒甚至阿秒时间尺度的关联机制，从时间维度理解分子化学键的断裂，并利用超短激光脉冲控制分子解离过程中电子在不同原子核上的分布，从而实现化学反应的相干控制。

5InP/InAs Heterostructure Nanowires towards Telecom-band Optoelectronic Devices

报告人：章国强，NTT Corporation

时间：12月26日（周四）10:00

单位：中国科学院物理研究所

地点：M楼236会议室

One motivation for the very intense research in III-V compound semiconductor nanowire field is that nanowire structures can offer new opportunities to main-stream semiconductors. In this talk, firstly, I will describe a CMOS-compatible synthesis approach, i.e. gold-free indium-particle-catalyzed (or self-catalyzed) vapor-liquid-solid growth mode. The approach enables the growth of InP/InAs heterostructure nanowire and lasing in telecom band at room temperature. We have also realized mid-IR lasing by using InAs nanowires with hexagonal crystalline structure. Controllable formation of p-i-n structure along the axial direction enables light emitting diodes to operate at room temperature with telecom-band electroluminescence. A novel approach will then be described for site control of indium nanoparticle by self-assembly process for InP/InAs nanowire array. Finally, I will describe an exceptional growth phenomenon in self-catalyzed vapor-liquid-solid mode that the catalyst particle size can be continuously tailored by modulating III-V source flow ratio.

6Simulation of Quantum Many-body Physics with Neural Network Representation

报告人：Di Luo, UIUC

时间：12月26日（周四）10:00

单位：中国科学院物理研究所

地点：M830

Simulation of quantum many-body physics, such as looking for ground state properties and real time dynamics, plays an important role in the study of condensed matter physics and quantum computation. With recent advancement of machine learning, new methods have been proposed to enhance quantum many-body physics simulation. In the first half of this talk, I will present a new class of wave functions, neural network backflow (NNB). NNB directly dresses mean-field ground state by transforming the single-particle orbitals in a configuration-dependent way. It produces the anti-symmetry property of fermionic wave function and generalizes the standard backflow to arbitrary lattice. We benchmark NNB on a Hubbard model at intermediate doping, finding that it significantly decreases the relative error, restores the symmetry of both observables and single-particle orbitals. 

7希格斯玻色子性质的精确测量与预测

报告人：陈暄，清华大学

时间：12月26日（周四）10:30

单位：清华大学

地点：物理系理科楼C302报告厅

在顶夸克被发现之后，高能物理学家经过十七年时间在大型强子对撞机上确认了希格斯玻色子的存在。自此高能物理标准模型所预测的全部粒子都已经在实验室中被确认。未来十五年高能物理研究将进入确认希格斯玻色子精确性质的阶段。其中关于希格斯玻色子的横动量微分分布，衰变宽度以及三线势能结构的精确预测以及测量，将对验证超标准模型，发现新一代夸克和确定宇宙稳定性等重要课题提供确凿的理论和试验依据。本次报告将重点总结目前关于希格斯玻色子精确微分分布的实验及理论进展，并展望未来十五年大型强子对撞机上面临的机遇和挑战。报告将对希格斯玻色子在强子对撞机上各个主要产生机制的世界第一理论精度进行总结，并且展望未来次次次领头阶(N3LO)量子色动力学微扰修正的应用。

8Aspects of the SYK model

报告人：顾颖飞，Harvard University

时间：12月27日（周五）10:00

单位：中国科学院物理研究所

地点：M830

I would like to give an introduction to the Sachdev-Ye-Kitaev (SYK) model, including its role in deepening our understanding of quantum chaos and quantum entanglement. I will also discuss some of its variants, including the complex SYK model, and a family of higher dimensional lattice generalization.

9Probing the Higgs self-coupling with the ATLAS detector

报告人：Xiaohu SUN, University of Manchester

时间：12月27日（周五）14:00

单位：北京航空航天大学

地点：Room 316, Main Building, Xueyuanlu Campus

The discovery of the Higgs boson at the Large Hadron Collider (LHC) in the summer of 2012 has experimentally confirmed the Brout–Englert–Higgs (BEH) mechanism of electroweak symmetry breaking and mass generation. The BEH mechanism not only predicts the existence of a massive scalar particle, the Higgs boson, but also requires this scalar particle to couple to itself, which is not observed yet. Therefore, searching for the production of double Higgs bosons and measuring the Higgs boson self-coupling is a crucial examination of the BEH mechanism. Any deviation from the Standard Model predictions opens a window to new physics. Moreover, the form of the Higgs field potential, which generates the Higgs boson self-coupling after electroweak symmetry breaking, can have important cosmological implications for the early evolution of the Universe, involving, such as the predictions for vacuum stability and the models in which the Higgs boson acts as the inflation field. This talk will discuss the current status of probing the Higgs self-coupling with double Higgs boson searches and single Higgs boson differential cross p measurements using the ATLAS detector at the LHC.

10Tunneling dynamics between superconducting bound states at the atomic scale

报告人：黄浩楠，德国斯图加特马克思普朗克固体物理研究所

时间：12月26日（周四）9:30

单位：中科院物理研究所

地点：A楼二层会议室

A Yu-Shiba-Rusinov (YSR) state is a pair of in-gap states bound to magnetic impurities on a superconductor. While YSR states have received intensifying attention especially in the field of scanning tunneling microscopy (STM) due to its capability to resolve and measure the transport through single atom, the tunneling processes between YSR states still remain elusive. We are now able to controllably introduce YSR state of desired properties to the apex of the STM tip and measure the tunneling between the tip YSR state and a sample YSR state, which we call Shiba-Shiba tunneling. The resulting peak feature in current at the sum of the two YSR energies shows a blockade when increasing conductance, which renders YSR tip a general probe of the single level lifetime at the atomic scale. Furthermore, combining the direct and thermal assisted Shiba-Shiba processes, we are able to extract the spin dynamics of the system.

11叶片单晶生长的工程控制理论与实践

报告人：李建国，上海交通大学先进材料与凝固研究所

时间：12月27日（周五）10:00

单位：中科院物理研究所

地点：M楼236会议室

与常规物理意义上的单晶不同，发动机叶片单晶是以发达的树枝状生长的近终成形构件。要获得特定取向的完整的叶片单晶，需要对选晶和生长阶段进行精细控制。然而关于单晶生长的理论仅能提供叶片单晶生长的部分必要条件。本研究证明传统的选晶方法具有本征的低成功率，需要彻底改变；通过对生长过程中枝晶受力和变形行为的分析，建立了以液/固界面宏观曲率为控制条件的避免枝晶变形超差的理论模型；通过对单晶生长过程中热流随叶片截面变化的分析，建立了以等热流为条件的单晶生长抽拉速度的控制方程。提出了单晶炉温度场质量指数和固液界面位置波动指数两个无量纲参数，可以定量表达叶片单晶生长装备的技术和质量水平。基于建立的理论模型，发展了新的叶片单晶生长装备和自适应控制系统，在单晶叶片生产中获得了应用。

更多报告信息：中国物理学会期刊网学术讲座列表

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