X射线激发荧光光谱仪的建立及闪烁晶体发光表征

利用X射线作为激发光源,自行组装并实现计算机控制的X射线激发荧光光谱仪.介绍了X射线激发荧光光谱仪的建立及其结构特性.该仪器具有时间分辨率高、测量动态范围大、使用方便等优点,可应用于晶体、粉末和液体等各种样品的测量,该仪器同时还具有很强的扩展性.     

Magnetotransport Properties of a Nodal Line Semimetal TiSi

We report the magnetoresistance(MR), de Haas-van Alphen(dHvA) effect and Hall effect measurements on a single crystal of TiSi, which is predicted to be a nodal line semimetal. With application of a magnetic field, a metal-to-insulator-like transition in ρ(T) and a nonsaturating MR are observed at low temperatures. The dHvA oscillations reveal a small Fermi-surface pocket with a nontrivial Berry phase. The analysis of the nonlinear Hall resistivity shows that TiSi is a multiband system with low carrier densities and high mobilities. All these results unambiguously prove the existence of Dirac fermions in TiSi.     

角分辨光电子能谱应用于固体物理学教学实践的探讨

角分辨光电子能谱是研究物质电子能带结构目前最先进的谱学仪器,在凝聚态物理学以及材料科学等领域的研究中占据重要地位.近年来,尽管越来越多的角分辨光电子能谱进入国内高校和科研院所,但角分辨光电子能谱价格高昂,结构复杂,因而很少将其应用于本科生教学的探索和实践.探讨了角分辨光电子能谱应用于本科生物理学教学实践的必要性和可行性,并讨论了具体的教学内容设计和实施,包括以物理学最新科研成果为课堂导入,开展材料电子能带结构的实验测试原理讲解、单晶的生长和单晶样品的展示,参观实验室和参与实验,激发本科生对物理学知识的学习热情和渴望,促使学生构筑清晰的物理学图像,提升对固体物理学知识的理解.     

Negative Longitudinal Magnetoresistance in the (8-Axis Resistivity of Cd

We report a systematic study on magnetotransport properties of the single crystal of cadmium(Cd). When the applied magnetic field B is perpendicular to the current I, the resistivities for both directions(I ‖ a, I ‖ c) show field induced metal-to-insulator-like transitions. The isothermal magnetoresistance(MR) at low temperatures increases approximately as the square of the magnetic field without any sign of saturation, and reaches up to 1140000% and 58000% at T = 2 K and B = 9 T for I ‖ a and I ‖ c, respectively. As the magnetic field rotates to parallel to the current, no sign of negative MR is observed for I ‖ a, while an obvious negative MR appears up to-70% at 2 K and 9 T for the current flowing along the c-axis, and the negative longitudinal MR shows a strong dependence of the electrode position on the single crystal. These results suggest that the negative longitudinal MR is caused by the dislocations formed in the process of crystal growing along the c-axis. Further studies are needed to clarify this point.     

用EXAFS方法研究钨酸铅晶体的缺陷结构

钨酸铅晶体具有很强的结构敏感性,导致复杂的缺陷现象.本研究试从微结构的角度阐明钨酸铅晶体的退火过程和异价离子掺杂机制.实验方法包括光吸收谱(以及红外谱),阻抗谱,X射线光电子能谱,和EXAFS分析.其中EXAFS信号能够给出配位原子种类,数量和距离等结构信息,可以发挥十分重要的作用.简述了2002年度北京同步辐射装置EXAFS工作站上完成的钨酸铅晶体缺陷研究工作中取得的主要结果.     

Electronic Structure of the Weak Topological Insulator Candidate Zintl Ba3Cd2Sb4

One of the greatest triumph of condensed matter physics in the past ten years is the classification of materials by the principle of topology.The existence of topological protected dissipationless surface state makes topological insulators great potential for applications and hotly studied.However,compared with the prosperity of strong topological insulators,theoretical predicted candidate materials and experimental confirmation of weak topological insulators(WTIs) are both extremely rare.By com...