选区外延生长的PbTe-超导杂化纳米线:一个可能实现拓扑量子计算的新体系

半导体-超导体杂化纳米线是用于研究马约拉纳零能模和拓扑量子计算的主要平台之一,而基于Ⅲ-Ⅴ族半导体InAs和InSb的纳米线则是当前此方向研究的主流材料体系.尽管经过多年制备技术的改进和优化,样品中过多的缺陷和杂质仍是阻碍此方向进一步发展的核心问题.近年来,一个新的马约拉纳纳米线候选体系——Ⅳ-Ⅵ族半导体PbTe-超导杂化纳米线吸引了很大关注并获得了快速的研究进展.PbTe的介电常数巨大,且具有晶格匹配的衬底,这些优势使其有潜力突破纳米线样品质量提升的瓶颈,成为马约拉纳零能模的研究和拓扑量子计算实现的理想平台.本文将简单介绍最近几年在PbTe纳米线和PbTe-超导杂化纳米线器件的选区分子束外延生长、输运性质研究方面取得的重要进展,并对这种新的马约拉纳纳米线候选体系的优势、问题及基于其实现拓扑量子计算的前景进行讨论.     

Revisit to frozen-in property of vorticity

Considering some simple topological properties of vorticity vector, the frozen-in property of vorticity herein is revisited. A vortex line, as is analogous to velocity vector along a streamline, is defined as such a coincident material(curve) line that connects many material fluid elements, on which the local vorticity vector for each fluid element is also tangent to the vortex line. The vortex line evolves in the same manner as the material line that it is initially associated with. The vortex line and the material line are both oriented to the same directions, and evolve with the proportional magnitude, just like being ‘frozen' or ‘glued' to the material elements of the fluid under the barotropic assumption. To relax the limits of incompressible and barotropic atmosphere, the frozen-in property is further derived and proved in the baroclinic case. Then two effective usages are given as examples. One is the derivation of potential vorticity conservation from the frozen-in property in both barotropic and baroclinic atmospheres, as a theory application, and the other is used to illuminate the vorticity generation and growth in ideal cases and real severe weather process, e.g., in squall line, tornado, and other severe convection weather with vortex. There is no necessity to derive vorticity equation, and this method is very intuitive to explain vorticity development qualitatively, especially for fast analysis for forecasters. Certainly, by investigating the evolution of vortex line, it is possible to locate the associated line element vector and its development on the basis of the frozen-in property of vorticity. Because it is simple and visualized, it manifests broad application prospects.     

五维自动调整差动共焦间隙测量方法

为精确、快速测量镜组内各透镜间的轴向间隙,提出一种基于五维自动调整的差动共焦间隙测量方法。该方法根据CCD探测器实时获取的光斑信号检测被测镜组光轴的平移偏差与倾斜偏差,依据偏差信息、通过五维自动调整技术实现镜组高精度调整,再利用差动共焦高精度层析定焦和镜组内部光线追迹实现轴向间隙高精度测量。分析和实验表明,本方法可以有效提高姿态调整效率3.4倍,透镜间隙重复测量精度可达到0.53μm。该方法为实现镜组间隙的快速高精度测量提供了有效途径,同时还为透镜的中心厚度、焦距、半径等多种参数快速高精度测量提供了有效方法。     

基于亲电/亲核反应描述符的气体介质绝缘强度预测

研究分子微观参数与气体介质绝缘强度的关联,可为SF₆替代气体筛选提供方向.本文基于密度泛函理论,采用M06-2X泛函与def2系列基组,计算了73种气体分子的亲电/亲核反应描述符,包括轨道能量参数、概念密度泛函理论的参数、不同电子概率密度等值面的静电势参数等;分析了各描述符与气体介质绝缘强度的相关性,以及描述符的独立性,最终提出了绝缘强度预测模型.最低空轨道能量、正负静电势表面积、静电势平均偏差、简缩局部亲电指数最小值与绝缘强度相关性较强,且彼此间相关性较低.预测模型在电子概率密度0.0002 a.u.时精度最优,其可决系数R²为0.809,均方误差MSE为0.096.     

松油醇-月桂酸低共熔溶剂理化性质与萃取丁醇的性能研究

研究了松油醇-月桂酸憎水性低共熔溶剂DES(deep eutectic solvent)的合成,采用红外光谱FT-IR和热重-差示扫描量热法TGA-DSC等手段对DES结构进行了表征,并测试了所合成DES的熔点、挥发性、憎水性和折光率,以及粘度和密度与温度的关系.实验结果表明,比例合适的松油醇-月桂酸DES不仅憎水性好...     

Hard Superconducting Gap in Pb Te Nanowires

<正>Semiconductor nanowires coupled to a superconductor provide a powerful testbed for quantum device physics such as Majorana zero modes and gate-tunable hybrid qubits. The performance of these quantum devices heavily relies on the quality of the induced superconducting gap. A hard gap,     

Sn类钙钛矿太阳电池薄膜的掺杂改性研究

采用一步法分别制备了Sn类CH3NH3Sn I3和Pb类CH3NH3Pb I3钙钛矿太阳电池薄膜材料,并对其表面形貌、微观结构、吸收光谱和电池器件性能进行了表征和测试。研究结果表明:Sn类钙钛矿材料的吸收光谱相对于Pb类钙钛矿材料发生了明显的红移,吸收截止波长从800 nm上升到950 nm左右,光学带隙由1.45 e V降低至1.21 e V左右;Sn类钙钛矿材料的光谱吸收范围明显扩大,但吸收强度有所降低,相应太阳电池器件的光电转换效率也明显低于Pb类钙钛矿太阳电池,分别为2.05%和6.71%。而Br的掺杂可使Sn类钙钛矿材料带隙变宽,吸收光子能量增大,电池器件的开路电压也相应提高。当Br含量由0增加至完全替代I时,Sn类钙钛矿材料逐渐由黑褐色转变为黄色,光学带隙增大至1.95 e V,但吸收截止波长由950 nm降低至650nm。值得提及的是当Br含量为0.5时,电池器件的光电转换效率可由最初的2.05%提升至2.94%。     

光催化剂SnC2O4的合成及其可见光催化活性

以(NH4)2C2O4为沉淀剂,采用直接沉淀法合成了新型光催化剂SnC2O4粉末.通过X射线粉末衍射、扫描电镜、紫外-可见分光光度计及荧光分光光度计等手段对样品的物相结构、微观形貌以及光吸收性能等进行了分析表征.结果表明:所制备的样品为单斜白钨矿型SnC2O4,空间群为C2/C(15).样品的微观形貌为不规则多面体,其禁带宽度为3.44 eV.光致发光光谱表明样品内部可能有大量的氧空位和其它缺陷.以甲基橙为模拟染料废水对SnC2 O4样品的光催化活性进行了评价.当甲基橙染料的浓度为40 mg/L,SnC2 O4光催化剂的投加量为40 mg/50 mL时,在模拟可见光照射下,甲基橙降解率可达99.1;,且光催化降解反应符合一级动力学方程.此外,通过引入活性物种捕获剂证明·O2-在光催化降解甲基橙反应中起重要作用.     

Accelerated oxygen precipitation in fast neutron irradiated Czochralski silicon

Annealing effect of the oxygen precipitation and the induced defects have been investigated on the fast neutron irradiated Czochralski silicon （CZ-Si） by infrared absorption spectrum and the optical microscopy. It is found that the fast neutron irradiation greatly accelerates the oxygen precipitation that leads to a sharp decrease of the interstitial oxygen with the annealing time. At room temperature （RT）, the 1107cm^-1 infrared absorption band of interstitial oxygen becomes weak and broadens to low energy side. At low temperature, the infrared absorption peaks appear at 1078cm^-1, 1096cm^-1, and 1182cm^-1, related to different shapes of the oxygen precipitates. The bulk microdefects, including stacking faults, dislocations and dislocation loops, were observed by the optical microscopy. New or large stacking faults grow up when the silicon self-interstitial atoms are created and aggregate with oxygen precipitation.     

载入树状分子内部的纳米金修饰玻碳电极的制备及其对亚硝酸根的电化学测定

建立了一种简单、可靠的基于载入树状分子内部的纳米金修饰电极用于亚硝酸根测定的电化学分析方法.将壳聚糖(Chit)修饰在玻碳电极表面,在偶联活化剂碳二亚胺存在的条件下,4.5代羧基末端的树状分子(Dendrimer)通过其外围的羧基与壳聚糖的氨基形成酰胺键而连接在电极表面.Au(Ⅲ)通过与树状分子内部氮的配位作用被结合在...