Remarkable progress has been made in the development of YBa2Cu3O7−δ (YBCO)-based coated conductors, and the problems of continuous processing of commercially viable tape lengths are being rapidly solved by companies around the world. However, the current carried by these tapes is presently limited to about 100A for a 1-cm-wide tape, and this is due to a rapid decrease of critical current density (Jc) as the coating thickness is increased. We have now overcome this problem by separating relatively thin YBCO layers with very thin layers of CeO2. Using this multilayer technology, we have achieved Jc values on metal substrates of up to 4.0MA∕cm2 (75K, self-field) in films as thick as 3.5μm, for an extrapolated current of 1400A∕cm width.

We report magneto-transport studies of topological insulator Bi 2 Te 3 thin films grown by pulsed laser deposition. A non-saturating linear-like magneto-resistance (MR) is observed at low temperatures in the magnetic field range from a few Tesla up to 60 Tesla. We demonstrate that the strong linear-like MR at high field can be well understood as the weak antilocalization phenomena described by Hikami-Larkin-Nagaoka theory. Our analysis suggests that in our system, a topological insulator, the elastic scattering time can be longer than the spin-orbit scattering time. We briefly discuss our results in the context of Dirac Fermion physics and 'quantum linear magnetoresistance'.

Carbon nanotubes (CNTs) are much stronger than any existing material. To fully utilize their extremely high strength, carbon-nanotubes must be spun into continuous fibers. [1][2][3] The most efficient way to produce commercial-scale CNT fibers is by the five-thousand-years-old cotton-based spinning technology.[4] Therefore, it is technologically attractive to produce CNT materials that have spinning properties similar to cotton. Here we report a new form of CNT material, CNT cotton, that is made of ultralong individual CNTs. This CNT cotton is analogous to conventional cotton in many aspects including the color and fluffiness, and is found favorable for spinning. It is found that the CNT cotton is hydrophobic, and is composed of low spatial density and ultra-long individual CNTs. Figure 1a is a photograph of fluffy and gray CNT cotton on a quartz support (15 mm × 35 mm). The CNT cotton has very low density with large space between individual CNTs, making it very similar to conventional cotton in terms of structural form. The gray color is surprising because all other CNT materials are black. This gray color is caused by the unique low spatial density of nanotubes in the CNT cotton, as well as a light-scattering effect. From the side view (Fig. 1b), we can see a 2 mm thick CNT cotton above the support, indicating that the CNT cotton is composed of long (at least millimeters) individual CNTs.The CNT cotton is also found to be hydrophobic. As shown in Figure 2a, a water droplet with a diameter of 2.5 mm was suspended on the CNT cotton. It sank into the CNT cotton because of its weight, but maintained a quasi-spherical shape. After the water-droplet was completely evaporated, the morphology of the CNT cotton was examined by scanning electron microscopy (SEM). The CNTs in the area that supported the water droplet were rearranged into a web-like mesh (see Fig. 2b), but the CNTs underneath the web still retained the cotton form (Fig. 2c), further confirming the hydrophobic behavior of CNT cotton.Catalytic chemical vapor deposition (CVD) [5] was used to synthesize the CNT cotton.

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