理学院数理讲坛（2017年第22-26讲）
报告题目1：Polarization splitter of surface polaritons
报告人： 王慧田教授 南京大学
报告时间：2017年6月17日 下午 1:00
报告地点：龙赛理科楼北311
报告摘要：We investigate surface polaritons (SPs) at the interface associated with anisotropic metamaterials. The existence conditions and handednesses of s- and p-polarized SPs are discussed in detail, which reveal that anisotropy is necessary for coexistence of s- and p-polarized SPs. We explore the reflection and transmission properties of SPs across the boundary separating two interfaces and then find the scaling relations that ensure the elimination of the parasite out-of-plane scattering of SPs. The reflection and transmission coefficients, the Brewster’s angle, and the critical angle of total reflection are developed. We propose a compact kind of polarization SP splitter, and its functional characters can be tuned by artificially designed constitutive parameters.
报告人简介：王慧田，南京大学特聘教授。聘任岗位：光学。博士生导师，2008年7月调入南开大学，任南开大学物理科学学院院长，博士生导师。1964年10月出生，“奖励计划”特聘教授，南京大学物理系/固体微结构物理国家重点实验室教授，博士生导师。
报告题目2：Anisotropic spin model of strong spin-orbit-coupled triangular antiferromagnets
报告人： 王孝群教授 上海交通大学
报告时间：2017年6月17日 下午 1:40
报告地点：龙赛理科楼北311
报告摘要：Motivated by the recent experimental progress on the strong spin-orbit-coupled rare-earth triangular antiferromagnet, we analyze the highly anisotropic spin model that describes the interaction between the spin-orbit-entangled Kramers' doublet local moments on the triangular lattice. We apply the Luttinger-Tisza method, the classical Monte Carlo simulation, and the self-consistent spin wave theory to analyze the anisotropic spin Hamiltonian. The classical phase diagram includes the 120 degrees. state and two distinct stripe-ordered phases. The frustration is very strong and significantly suppresses the ordering temperature in the regimes close to the phase boundary between two ordered phases. Going beyond the semiclassical analysis, we include the quantum fluctuations of the spin moments within a self-consistent Dyson-Maleev spin-wave treatment. We find that the strong quantum fluctuations melt themagnetic order in the frustrated regions. We explore the magnetic excitations in the three different ordered phases as well as in strong magnetic fields. Our results provide a guidance for the future theoretical study of the generic model and are broadly relevant for strong spin-orbit-coupled triangular antiferromagnets such as YbMgGaO4, RCd3P3, RZn3P3, RCd3As3, RZn3As3, and R2O2CO3.
报告人简介：王慧田，南京大学特聘教授。聘任岗位：光学。博士生导师，2008年7月调入南开大学，任南开大学物理科学学院院长，博士生导师。1964年10月出生，“奖励计划”特聘教授，南京大学物理系/固体微结构物理国家重点实验室教授，博士生导师。王孝群， 现任上海交通大学物理与天文系教授、系主任, 国家杰出青年基金获得者。研究兴趣：低维强关联、介观系统性质的电子、磁性和输运特性以及量子信息等方面的理论研究；一些数值模拟方法的探讨、发展与应用。以王孝群教授为学术带头人的中国人民大学“计算物理方法的发展及其在新奇量子现象研究中的应用”团队入选2007年度“和创新团队发展计划”创新团队。
报告题目3： Hybrid Crystalline sp2-sp3 Carbon as a High-Efficiency Solar Cell
报告人： 龚新高教授 复旦大学
报告时间：2017年6月17日 下午 2:20
报告地点：龙赛理科楼北311
报告摘要：Carbon is a versatile element that has allotropes with both sp2 (graphene) and sp3 (diamond) bonding. However, none of the allotropes can be used as light-absorber materials in solar cells due to either too large or too small band gap. Here, we propose a novel concept that enables a tunable band gap of carbon phases with sp2 carbon atoms within a sp3 carbon structure. The tunability is due to the quantum confinement effect. By embedding the sp2 atoms within the sp3 structure, we can design new carbon allotropes with ideal optical properties for optoelectronic applications. Five carbon allotropes incorporated this structural feature were identified by combining this new concept with our freshly developed multi-objective inverse band structure design approach. They all have proper band gaps for optical absorption, and the simulated photovoltaic efficiency of C10-C is even higher than conventional absorber materials such as GaAs, which indicates that C10-C with mixed sp2-sp3 hybridization may have potential application as light-absorber material in electronic and optoelectronic devices.
报告人简介：龚新高，复旦大学物理系教授, 计算物质科学教育部重点实验室主任；1993年5月毕业于中国科学院固体物理研究所获得理学博士学位。 2000 年调入复旦物理系任教授。1999 年获得国家杰出青年基金， 2006 年上海市学术带头人。主要从事计算凝聚态物理和计算材料科学的研究。研究重点是物质体系的物性预测和动力学模拟。发现镓同时具有分子性和金属性是固体镓和流体镓表现出奇异物性的本质原因，解决了困扰多年的有关镓的物性及流体结构的问题。发现掺杂或带电可提高团簇的稳定性，为合成团簇材料提供了新的可能途径。设计和预言了多个特殊稳定团簇及其固体的结构。发现小团簇在固体表面快速扩散的新机制－滚动。在发展分子动力学方法、建立新的优化方法以及拟合原子相互作用势等研究中取得了积极的进展。
报告人： 郑波 教授 浙江大学
报告时间：2017年6月17日 下午 3:00
报告地点：龙赛理科楼北311
报告摘要：With Monte Carlo simulations, we investigate the relaxation dynamics with a domain wall for magnetic systems at the critical temperature. The dynamic scaling behavior is carefully analyzed, and a dynamic roughening process is observed. For comparison, similar analysis is applied to the relaxation dynamics with a free or disordered surface。
报告人简介：郑波教授, 浙江大学近代物理中心博士生导师，长江特聘教授/博士生导师/国家杰出青年基金获得者。早期研究方向为量子场论，如格点规范理论、随机量子化等。1994年以来主要兴趣在计算物理、非平衡态统计物理、软凝聚态物理和复杂系统等相关学科。应用 Monte Carlo 方法，在远离平衡态动力学的数值模拟方面取得创造性研究成果。率先提出的短时动力学测量方法可应用于连续相变和弱一级相变系统、无序系统、量子自旋系统和超流超导系统等。至今在SCI收录的学术刊物发表论文九十余篇，其中五篇发表于Physical Review Letter，论文的SCI引文数近2000篇次。近期高度关注金融物理和生物物理等交叉学科。
报告题目5： Pressure-induced structural transformation of CdSe nanocrystals studied with molecular dynamics
报告人： 孙得彦研究员 华东师范大学
报告时间：2017年6月17日 下午 3:40
报告地点：龙赛理科楼北311
报告摘要：We have studied the pressure-induced structural transformation of CdSe nanocrystals using constant pressure molecular dynamics simulations for finite system. We have observed the transformation from wurtzite to rocksalt structure, the process of transformation is strongly dependent on the shape and size of the nanocrystals, and transformation pressure decreases with increasing nanocrystal size. The spherical CdSe nanocrystals studied undergo nonuniform deformation, while the faceted ones undergo uniform deformation. The reverse transformation from rocksalt backward to wurtzite structure of the nanocrystals happens below 1GPa at room temperature, and the width of the transformation decreases as the temperature increases.
报告人简介：孙得彦, 华东师范大学物理与材料科学学院研究员。1998年在中国科学院固体物理研究所获得博士学位。2001年至2003年在美国西北大学材料科学与工程系作博士后研究。2004年调入华东师范大学物理系任教授，博士生导师。2004年获上海市教委曙光学者称号。主要科研成果包括：从理论上预言了一种新的滚动扩散机制；提出一种新的等压分子动力学方法；发现了固液界面的结构依赖性；从理论上预言一种 新的团簇熔化行为等。主持国家自然科学基金重点子项目；国家自然科学基金面上项目；上海市教委曙光人才基金；上海市科委浦江人才基金等。