一维介观金属环系统中的量子电流

针对处于外磁场中的一维介观环系统,假设在电荷空间中具有变换的对称性,通过求解电流算符的本征值方程,给出系统中的量子电流关系,分析和研究一维介观金属环中量子电流的性质.结果表明,量子电流不仅与外磁场、介观金属环参数有关,而且还明显地依赖于电荷的量子化性质.     

外磁场中介观金属环的量子电流和能谱及其量子涨落

针对处于外磁场中的介观金属环系统,假设在电荷空间中具有变换的对称性,通过求解本征值方程给出系统的量子电流、能谱关系;利用最小平移算符的性质等,计算介观金属环中电流和能量的量子涨落.研究介观金属环中量子电流、量子能谱的性质,分析影响量子涨落的因素.结果表明,量子电流、量子能谱不仅与外磁场、介观金属环电参数有关,而且还明显地依赖于电荷的量子化性质.     

1维格子组成环形带绝缘体上的持续电流

通过磁通的介观正常金属环存在持续电流.最近,有人指出在由能带绝缘体制成的环中也存在持续电流,持续电流是由完全占满价带的电子产生的.用环形1维格子的布洛赫态组成1维环的电子态的方法,研究了环形能带绝缘体组成的环里的持续电流,推导出了由任意价带的绝缘体组成的1维环中的持续电流.     

无序对介观环持续电流的影响

研究处在非均匀磁场中的一维介观环持续电流受无序的影响问题，得到非对角无序对持续电流在更大的衰减效应。     

正常金属环中持续电流计算公式的经典动力学推导

本文介绍了正常金属环中持续电流计算公式的一种新的推导方法。该方法基于经典动力学理论,与传统方法相比能够充分地揭示公式背后所隐藏的物理图像。希望本文提出的这一方法能够帮助人们更好地理解与掌握正常金属环中持续电流的计算公式。     

一维非金属介观环的持续电流

利用Ｚｏｕ－Ａｎｄｅｒｓｏｎ的电荷自旋分离方案，通过具有一定掺杂的大ＵＨｕｂｂａｒｄ模型研究非金属型的一维介观环的持续电流．结果发现，电荷流振幅受Ｓｐｉｎｏｎ场序参量的影响，自旋流振幅受Ｈｏｌｏｎ场序参量影响和材料掺杂浓度δ的影响．     

介观孔对介观超导圆盘中涡旋态的影响研究

目的计算带孔介观超导圆盘中不同涡旋态下超导序参量分布,分析介观孔对超导圆盘涡旋态的影响。方法求解Ginzburg-Landau方程。结果计算了带孔介观尺度超导圆盘中涡旋态的超导电子对密度分布,并与不带孔的介观超导圆盘的情况进行了比较。结论介观孔改变了介观超导圆盘中超导序参量的分布特征。     

铁磁自旋波对Texture介观环中持续电流的影响

利用自旋波理论研究某种晶体结构中介观环的持续电流．发现自旋波的量子涨落将影响介观中的持续电流、电流振幅随温度的变化由赝Ｄｅｂｙｅ－Ｗａｌｌｅｒ系数决定．在低温极限下．赝Ｄｅｂｙｅ－Ｗａｌｌｅｒ系数仍不为零．     

铁磁自旋波对介观环中持续电流的影响：Ⅱ.Peierls失稳中magnon的作用

研究在Ｔｅｘｔｕｒｅ结构中自旋波的量子涨落（ｍａｇｎｏｎ）对具有Ｐｅｉｅｒｌｓ失稳性的介观环持续电流的影响，结果表明由于能隙的出现而使持续电流进一步的减少     

电子—声子相互作用对金属介观环中持续电流的影响

在连续模型中研究了电子－声子相互作用对一维金属介观环中由磁通Φ诱发的持续电流的贡献．持续电流随磁通Φ的变化具有周期性．周期为磁通量子Φ０＝ｈ／ｅ．研究表明,电子－声子相互作用不仅降低系统能量而且对持续电流有抑制作用．持续电流与系统中的电子数（Ｎ）有明显的依赖关系．当（Ｎ）增加到足够大时,持续电流趋于零．     

Fault Current Limitation with Superconducting YBCO Thin Films

The behavior of YBCO/metal bilayers under transport currents was explored in the framework of fault current limitation (FCL). Properties of the superconducting-normal transition were first studied phenomenologically during sweep current experiments. For current rates higher than 500A/s, the transition into the normal state was based on non-thermal phenomena and was characterized by a flux creep regime ended by a jump into the normal state. At lower sweep rates, a total diversion of the current in the metallic shunt was observed for temperatures higher than 85 K. In this regime, a partial recovery of the superconducting state took place due to a finite thermal resistance between the superconducting and the metallic films. These two properties of partial diversion into the shunt and of fast switching for a quick rise of the current during a default were exploited for current limitation at 77 K. FCL experiments at 50 Hz show that YBCO/Au bilayers limit the current in about 1 ms at a value of 2.5/c by developing electrical fields as high as 3 kV/m. Moreover, a recovery of the zero resistance state could occur under rated mode. A straightforward application of this property would be the transformer connection. Finally, results on DC current limitation and recovery under nominal mode were presented for the first time.     

介观尺度超导体的超导电性

在 Ginzburg-Landau 理论框架内,发展了一种解析的处理方法研究了介观超导体的超导电性。     

Symmetry-induced formation of antivortices in mesoscopic superconductors

Recent progress in nanotechnology has stimulated interest in mesoscopic superconductors as components for quantum computing and cryoelectronics. The critical parameters for superconductivity (current and field) of a mesoscopic sample are determined by the pattern of vortices in it, which in turn is controlled by the symmetry imposed by the shape of the sample (see ref. 1 and references therein). Hitherto it has been unclear what happens when the number of vortices is not consistent with the natural symmetry. Here we show that additional vortex-antivortex pairs nucleate spontaneously so as to preserve the symmetry of the sample. For example, in a square with three vortices, the spontaneously generated pair, along with the original three vortices, distribute themselves so that the four vortices sit in the four corners, with the antivortex in the centre. The measured superconducting phase boundary (of superconducting transition temperature Tc versus magnetic field strength) is in very good agreement with the calculations, giving direct experimental evidence for these symmetry-induced vortex-antivortex pairs. Vortex entry into the sample is also changed: vortices enter a square in fours, with antivortices generated to preserve the imposed vorticity. The symmetry-induced nucleation of antivortices is not restricted to superconductors, but should also apply to symmetrically confined superfluids and Bose-Einstein condensates.     

离散电荷介观LC电路中的电荷与电流的时间演化

主要通过考虑介观电容的耦合能，对离散电荷介观LC电路中的电荷与电流的动力学行为进行了研究。结果表明：电荷与电流的时间演化函数由雅可比椭圆函数替代，而且在电路中显示周期性压缩效应。     

Current Limiting Characteristic Analysis of Magnetic-controlled Switcher Type Fault Current Limiter

A novel magnetic-controlled switcher type fault current limiter （FCL） based on the topology of the saturated iron core high temperature superconducting FCL is proposed. The magnetic field distribution of the FCL iron core is analyzed by FEA software ANSYS. The current limiting characteristic is investigated by both 3-D field-circuit coupled simulation and Matlab. The experiments on the 220 V/50 A test model show that the FCL can limit the fault current swiftly and effectively,and the FCL has the advantages of simple and reliable structure, flexible control strategy. The simulation and experimental results prove that the theoretical expectation and current limiting performance is satisfactory for practical use.     

Local switching of two-dimensional superconductivity using the ferroelectric field effect

Correlated oxides display a variety of extraordinary physical properties including high-temperature superconductivity and colossal magnetoresistance. In these materials, strong electronic correlations often lead to competing ground states that are sensitive to many parameters--in particular the doping level--so that complex phase diagrams are observed. A flexible way to explore the role of doping is to tune the electron or hole concentration with electric fields, as is done in standard semiconductor field effect transistors. Here we demonstrate a model oxide system based on high-quality heterostructures in which the ferroelectric field effect approach can be studied. We use a single-crystal film of the perovskite superconductor Nb-doped SrTiO3 as the superconducting channel and ferroelectric Pb(Zr,Ti)O3 as the gate oxide. Atomic force microscopy is used to locally reverse the ferroelectric polarization, thus inducing large resistivity and carrier modulations, resulting in a clear shift in the superconducting critical temperature. Field-induced switching from the normal state to the (zero resistance) superconducting state was achieved at a well-defined temperature. This unique system could lead to a field of research in which devices are realized by locally defining in the same material superconducting and normal regions with 'perfect' interfaces, the interface being purely electronic. Using this approach, one could potentially design one-dimensional superconducting wires, superconducting rings and junctions, superconducting quantum interference devices (SQUIDs) or arrays of pinning centres.