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Topological insulators are insulating materials that display conducting surface states protected by time-reversal symmetry (1,2), wherein electron spins are locked to their momentum. This unique property opens up new opportunities [...]

The doping of charge carriers into the Cu[O.sub.2] planes of copper oxide Mott insulators causes a gradual destruction of antiferromagnetism and the emergence of high-temperature superconductivity. Optimal superconductivity is achieved at a doping concentration p beyond which further increases in doping cause a weakening and eventual disappearance of superconductivity. A potential explanation for this demise is that ferromagnetic fluctuations compete with superconductivity in the overdoped regime. In this case, a ferromagnetic phase at very low temperatures is predicted to exist beyond the doping concentration at which superconductivity disappears. Here we report on a direct examination of this scenario in overdoped [La.sub.2-x][Sr.sub.x]Cu[O.sub.4] using the technique of muon spin relaxation. We detect the onset of static magnetic moments of electronic origin at low temperature in the heavily overdoped non-superconducting region. However, the magnetism does not exist in a commensurate long-range ordered state. Instead it appears as a dilute concentration of static magnetic moments. This finding places severe restrictions on the form of ferromagnetism that may exist in the overdoped regime. Although an extrinsic impurity cannot be absolutely ruled out as the source of the magnetism that does occur, the results presented here lend support to electronic band calculations that predict the occurrence of weak localized ferromagnetism at high doping. doi/ 10.1073/pnas.1007079107

The inductive method for measuring the critical current density in a high-temperature superconductor (HTS) has been investigated numerically. In the method, an ac magnetic field is generated by a small coil placed just above a HTS sample and, simultaneously, the third-harmonic voltage Va induced in the coil is measured. In order to simulate the inductive method, a numerical code has been developed for analyzing the time evolution of the shielding current density. By using the code, the [I.sub.o]--[V.sub.3] curves are determined and, subsequently, the critical current density is estimated. The results of computations show that, even if the power law is assumed as the J-E constitutive relation, the critical current density can be accurately estimated by the inductive method. In addition, it is found that, for both a film HTS and a bulk HTS, the assumed B-dependence of the critical current density can be successfully reproduced by the estimating formulas of the inductive method. Index Terms--Finite element methods, high-temperature superconductor (HTS), integration, simulation.

Finite-element method is used for examining the influence of various numerical parameters on the precision and the speed of ac loss computations in high-temperature superconductors. A new and simple self-check test is proposed for validating the computed ac losses and the behavior of the numerical solution near flux/current fronts is analyzed.

The influence of the current density (Jc) and magnetic flux density (B) on the losses in a superconductive tube fed by a transport current in incomplete current penetration is examined. The losses in the superconducting tube are calculated and compared with the measurements taken on a sample whose characteristic [J.sub.c](B) is already calculated.

A method of self field compensation in the electrical measurement of [J.sub.mc]([B.sub.ext]) (where [B.sub.ext] is an external magnetic flux density) is described for a superconducting tube. For compensating the self field effects, the results have shown that the internal tube current must be equal to one half of the tube current.

A Halbach permanent magnetic guideway (PMG) is presented for improving the levitation performance of high-temperature superconducting (HTS) magnetic levitation (maglev) vehicle. The studies have shown that an optimality criterion is used for evaluating the levitation performance for the HTS maglev vehicle.

The hysteresis characteristic of high-temperature superconductors (HTSs) has helped in proposing a new method for reducing the relaxation of the levitation force in the symmetrical levitation system. The studies have shown that for the unsymmetrical levitation system, one movement mode of the magnet can reduce the relaxations of the levitation force and guidance force synchronously, while the quantities of the levitation force and guidance force are changed little.

A new finite-element model is developed to study the electromagnetic and thermal behavior of high-temperature superconductor (HTS) for resistive fault current limiter applications. This model is simpler to use and fast due to coupling of electromagnetic and thermal equations in a single process.

We describe a new approach to the magnetic measurement of liver iron stores, using an instrument that incorporates a combination of permanent magnets and superconducting flux transformers. Instead of traditional low-transition-temperature superconductor (LTS) transformers, the susceptometer employs their high-transition-temperature (HTS) counterparts. This innovation substantially reduces the size and weight of the instrument, allowing the whole assembly to be scanned in a horizontal plane. We report engineering details of the HTS flux transformers, magnet assembly, field sensing, and scan mechanism, and present experimental data to show that scanning susceptometry can determine not only the susceptibility of cylindrical phantom models but also their diameters. We conjecture that further refinements of scanning susceptometry could lead to a form of susceptibility imaging that would enhance the accuracy of measurements of liver iron stores and also lead to new medical applications of the method. Index Terms--Density, flux transformer, high-[T.sub.c], imaging, phantom, scanning, storage iron, susceptibility.

An original semi-analytical method for computing the 2-D current distribution in conductors and superconductors of arbitrary shape is presented. It is based on the analytical relationships between current density, vector potential and magnetic flux density and shows a good agreement with the previous method.

Conduction-cooled high-temperature superconductor superconducting magnetic energy storage (SMES) is developed using a solenoid-type coil and cooled to about 20 K by conduction-cooled method. A series of tests are carried out to measure the performance of this SMES.

The gap between a superconductor and a permanent magnet varying with time in high-[T.sub.c] superconducting levitation system is studied. The results show that the drift velocity is dependent upon properties of superconductivity, initial disturbances, and applied excitations.

The drift of levitated body/suspended body in high-[T.sub.c] superconducting levitation systems under vibration numerically is studied. Results reveal that the drift phenomenon is characterized by judging the gap varying with time for a given levitation system.

The excitation testing of high temperature superconducting (HTS) coil with Bi2212 cables is examined for development of high energy density superconducting magnetic energy storage (SMES). Findings reveal the confirmation of sufficient thermal stability during the thermal runaway test.

The creation of a fast and complete non-mechanic turnout switch is examined for establishing a highly branched transportation network using the stable levitation of bulk high temperature superconductor (HTS). Results suggest the observation of a retarding behavior in the turnout switch without any critical limits for levitation and guidance.

The article discusses the design and operation of the laboratory-scale high temperature superconducting (HTS) Maglev launch system developed in the Applied Superconducting Laboratory (ASCLab) of Southwest Jiaotong University in China.

The article discusses the design and performance analysis of a linear permanent magnet synchronous motor for driving a small scale prototype Maglev vehicle. Results suggest that the linear driving system is capable of generating an appropriate driving force for the high temperature superconductor (HTS) Maglev vehicle prototype.

The shielding effect of high temperature superconducting (HTS) was used for examining the lift force in the magnetic levitation system. Findings reveal that a combination of three sets of the bulk/rail and the support ferromagnetic is instrumental in increasing the lift force.

The free vibration of the high temperature superconducting (HTS) Maglev vehicle model was investigated to study the dynamic properties of the HTS Maglev vehicle. Results suggest that free cooling height (FCH) is an effective parameter for automatic suppressing of the vibration of the HTS Maglev vehicle.

The stability of high temperature superconducting (HTS) power cable under fault current is examined. Findings reveal the determination of the stabilizer area for the practical HTS power cable for suppression of the bubble generation under the fault current.

The conceptual design of a 110 kV resistive superconducting fault current limiter (SCFCL) is discussed. A magnetic field triggered concept that offers high electrical fields during limitations and very high rated currents per High Temperature Superconducting (HTS) element is used for SCFCL.

The article examines the EMTDC model component for High Temperature Superconducting (HTS) power cable. The model component is capable of describing the transient change of resistance value at every one sampling time.

The article presents the computational two-dimensional and three-dimensional finite element analysis study of current induced quench (CIQ) and temperature induced quench (TIQ) in High Temperature Superconducting (HTS) coils. Findings reveal that pre-quench instability is practically undetectable with an insufficient amount of stabilizer for second-generation (2-G) HTS tapes.

The electrical properties of semiconducting tapes used for field grading applications in high voltage technology are examined. Findings reveal that the tapes have U-shaped temperature dependence of resistivity corresponding to metallic and insulator type character for temperatures over and below 170 K.

The first experiment on levitation and plasma with high temperature superconducting (HTS) magnet in the Ring Trap 1 (RT-1) plasma device is discussed. Results suggest the ability of the floating HTS magnet to operate in a persistent-current mode without cooling.

The study presents the numerical simulations of the permanent magnet method, which is employed for measuring the critical current density of the high-temperature superconducting (HTS) thin film. The analysis shows a linear relation between the critical current density and the maximum repulsive force.

A new computer based model is studied to analyze the electromagnetic behavior of various systems, including the high-temperature superconductors (HTS). The method is found to be very advantageous, as it can be also used to solve complex problems in complex geometries.

A numerical method for calculating the shielding current density in a high temperature superconducting (HTS) thin film is described. The results demonstrate the existence of a linear relationship between the critical current density and the maximum repulsive force.

The flux-dynamics of the high-temperature superconductors (HTS) with microscale irradiation-modified regions are described. The analysis reveals that these magnetic field detectors can be easily used for several other applications.

Several measurements and numerical simulations of the nonlinear magnetic diffusion in a Bi2212 high temperature superconducting (HTS) hollow cylinder are presented. These cylinders can be easily used in inductive fault current limiters and various other applications.

The fabrication of the Gd[Ba.sub.2][Cu.sub.3][O.sub.7-x] (GdBCO) and Y[Ba.sub.2][Cu.sub.3][O.sub.7-x] (YBaCuO) long coated conductors by the ion-beam deposition (IBAD) and pulsed laser deposition processes. The process is found to highly enhance the production speed and the critical current of these conductors.

The current transport properties of the 200 A-200 m-class ion-beam assisted deposition (IBAD)-[Y.sub.1][ba.sub.2][Cu.sub.3][O.sub.7-[delta]] (YBCO) coated conductor are explained. The values of the critical current densities are proved to be higher at low temperatures.

The analysis describes a recently launched experimental set up for measuring the AC losses of the high temperature superconductor (HTS) in the rotating magnetic field. The technique can be easily used to acquire the required frequency and the field within the rotating systems.

The characteristics of the AC losses in various stacked conductors that are composed of HTS coated conductors (CC's) with different magnetic substrates, are described. These losses can be easily reduced by stack arrangement of the conductors.

The effects of the magnetism of substrate on the AC transport current loss of a high temperature superconducting (HTS) conductor with ferromagnetic substrate are explained. The AC transport current loss is found to increase with the concentration of the magnetic flux in the substrate.

The study evaluates the effects of the superfluid helium on the superconducting properties of the Bi-2223 tapes, which are used for high temperature superconducting (HTS) inserts. The cooling of the tape with helium is found to lead to higher field contribution and more stability.