TABLE 53.4 Type II(High-Temperature Superconductors) Material T (K) Aab(nm) A, (nm) Eab ( INi, B, C Rb, CEo 33 YBa, Cu, O, 1350 Bi,Sr, Cacu, OB HgBaCaCu, O6 HgBa, Ca Cu,O resistance, even though the material is still superconducting. To fix this problem, type II superconductors are usually fabricated with intentional defects, such as impurities or grain boundaries, in their crystalline structure to pin the vortices and prevent vortex motion. The pinning is created because the defect locally weakens the superconductivity in the material, and it is thus energetically favorable for the normal core of the vortex to overlap the nonsuperconducting region in the material. Critical current densities usually quoted for practical type II materials, therefore, really represent the depinning critical current density where the Lorentz-like force can overcome the pinning force.(The depinning critical current density should not be confused with the depairing critical current density, which represents the current when the Cooper pairs have enough kinetic energy to overcome their correlation. The depinning critical current density is typically an order of magnitude less than the depairing critical current density, the latter of which represents the theoretical maximum for Je By careful manufacturing, it is possible to make superconducting wire with tremendous amounts of current carrying capacity. For example, standard copper wire used in homes will carry about 10A/m2, whereas a practical type II superconductor like niobium-titanium can carry current densities of 100A/m? or higher even in fields of several teslas. This property, more than a zero dc resistance, is what makes superconducting wire Defining Terms perconductivity: A state of matter whereby the correlation of conduction electrons allows a static current to pass without resistance and a static magnetic flux to be excluded from the bulk of the material. Related Topic 35. 1 Maxwell equations References A. Barone and G. Paterno, Physics and Applications of the Josephson Effect, New York: Wiley, 1982 R. J. Donnelly,"Cryogenics, "in Physics Vade Mecum, H L. Anderson, Ed, New York: American Institute of hysics, 1981 S. Foner and B. B Schwartz, Superconducting Machines and Devices, New York: Plenum Press, 1974 S. Foner and B. B Schwartz, Superconducting Materials Science, New York: Plenum Press, 1981 J. Knuutila, M. Kajola, H. Seppa, R Mutikainen, and J. Salmi, Design, optimization, and construction of a DC SQUID with complete flux transformer circuits, J. Low. Temp. Phys., 71, 369-392, 1988. K.K. Likharev, Dynamics of Josephson Junctions and Circuits, Philadelphia, Pa. Gordon and Breach Science Publishers, 1986 T P Orlando and K A Delin m上90 1991 Ruggiero and D A Rudman, Sup B. Schwartz and S. Foner, Superconducting Applications: SQUIDs and Machines, New York: Plenum Press, 1977. T. Van Duzer and C. W. Turner, Principles of Superconductive Devices and Circuits, New York: Elsevier North Holland. 1981 e 2000 by CRC Press LLC© 2000 by CRC Press LLC resistance, even though the material is still superconducting. To fix this problem, type II superconductors are usually fabricated with intentional defects, such as impurities or grain boundaries, in their crystalline structure to pin the vortices and prevent vortex motion. The pinning is created because the defect locally weakens the superconductivity in the material, and it is thus energetically favorable for the normal core of the vortex to overlap the nonsuperconducting region in the material. Critical current densities usually quoted for practical type II materials, therefore, really represent the depinning critical current density where the Lorentz-like force can overcome the pinning force. (The depinning critical current density should not be confused with the depairing critical current density, which represents the current when the Cooper pairs have enough kinetic energy to overcome their correlation. The depinning critical current density is typically an order of magnitude less than the depairing critical current density, the latter of which represents the theoretical maximum for Jc.) By careful manufacturing, it is possible to make superconducting wire with tremendous amounts of current￾carrying capacity. For example, standard copper wire used in homes will carry about 107 A/m2 , whereas a practical type II superconductor like niobium–titanium can carry current densities of 1010 A/m2 or higher even in fields of several teslas. This property, more than a zero dc resistance, is what makes superconducting wire so desirable. Defining Terms Superconductivity: A state of matter whereby the correlation of conduction electrons allows a static current to pass without resistance and a static magnetic flux to be excluded from the bulk of the material. Related Topic 35.1 Maxwell Equations References A. Barone and G. Paterno, Physics and Applications of the Josephson Effect, New York: Wiley, 1982. R. J. Donnelly, “Cryogenics,” in Physics Vade Mecum, H.L. Anderson, Ed., New York: American Institute of Physics, 1981. S. Foner and B. B. Schwartz, Superconducting Machines and Devices, New York: Plenum Press, 1974. S. Foner and B. B. Schwartz, Superconducting Materials Science, New York: Plenum Press, 1981. J. Knuutila, M. Kajola, H. Seppä, R. Mutikainen, and J. Salmi, Design, optimization, and construction of a DC SQUID with complete flux transformer circuits, J. Low. Temp. Phys., 71, 369–392, 1988. K. K. Likharev, Dynamics of Josephson Junctions and Circuits, Philadelphia, Pa.: Gordon and Breach Science Publishers, 1986. T. P. Orlando and K. A. Delin, Foundations of Applied Superconductivity, Reading, Mass.: Addison-Wesley, 1991. S. T. Ruggiero and D. A. Rudman, Superconducting Devices, Boston: Academic Press, 1990. B. B. Schwartz and S. Foner, Superconducting Applications: SQUIDs and Machines, New York: Plenum Press, 1977. T. Van Duzer and C. W. Turner, Principles of Superconductive Devices and Circuits, New York: Elsevier North Holland, 1981. TABLE 53.4 Type II (High-Temperature Superconductors) Material Tc (K) la,b (nm) lc (nm) ja,b (nm) jc (nm) LuNi2B2C 17 71 6 Rb3C60 33 300 3 YBa2Cu3O7 95 150 1350 3 0.2 Bi2Sr2CaCu2O8 85 25 500 4.5 0.2 Bi2Sr2Ca2Cu3O10 110 Tl2Ba2Ca2Cu3O10 125 HgBaCaCu2O6 115 150 2.5 HgBa2Ca2Cu3O8 135