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The Three Hallmarks of Superconductivity

The Three Hallmarks of Superconductivity. Macroscopic Quantum Effects. Complete Diamagnetism. Flux F. T>T c. T<T c. Magnetic Induction. 0. Flux quantization F = n F 0 Josephson Effects. T c. Temperature. Zero Resistance. I. V. DC Resistance. 0. T c. Temperature.

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The Three Hallmarks of Superconductivity

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  1. The Three Hallmarks of Superconductivity Macroscopic Quantum Effects Complete Diamagnetism Flux F T>Tc T<Tc Magnetic Induction 0 Flux quantization F = nF0 Josephson Effects Tc Temperature Zero Resistance I V DC Resistance 0 Tc Temperature

  2. Zero Resistance R = 0 only at w = 0 (DC) R > 0 for w > 0 E Quasiparticles 2D The Kamerlingh Onnes resistance measurement of mercury. At 4.15K the resistance suddenly dropped to zero Energy Gap 0 Cooper Pairs

  3. vacuum superconductor l l(T) l magnetic penetration depth B=0 surface screening currents l(0) T Tc The Yamanashi MLX01 MagLev test vehicle achieved a speed of 343 mph (552 kph) on April 14, 1999 l is independent of frequency (w < 2D) Perfect Diamagnetism Magnetic Fields and Superconductors are not generally compatible The Meissner Effect Super- conductor T>Tc T<Tc Spontaneous exclusion of magnetic flux

  4. What are the Limits of Superconductivity? Phase Diagram Jc Normal State Superconducting State m0Hc2 Tc Ginzburg-Landau free energy density Temperature dependence Currents Applied magnetic field

  5. S + + + + v v + + + + S WDebye is the characteristic phonon (lattice vibration) frequency N is the electronic density of states at the Fermi Energy V is the attractive electron-electron interaction A many-electron quantum wavefunction Y made up of Cooper pairs is constructed with these properties: An energy 2D(T) is required to break a Cooper pair into two quasiparticles (roughly speaking) Cooper pair size: BCS Theory of Superconductivity Bardeen-Cooper-Schrieffer (BCS) Cooper Pair s-wave ( = 0)pairing Spin singlet pair Second electron is attracted to the concentration of positive charges left behind by the first electron First electron polarizes the lattice http://www.chemsoc.org/exemplarchem/entries/igrant/hightctheory_noflash.html

  6. Where do we find Superconductors? Also: Nb-Ti, Nb3Sn, A3C60, NbN, MgB2, Organic Salts ((TMTSF)2X, (BEDT-TTF)2X), Oxides (Cu-O, Bi-O, Ru-O,…), Heavy Fermion (UPt3, CeCu2Si2,…), Electric Field-Effect Superconductivity (C60, [CaCu2O3]4, plastic), … Most of these materials, and their compounds, display spin-singlet pairing

  7. The High-Tc Cuprate Superconductors Layered structure – quasi-two-dimensional Anisotropic physical properties Ceramic materials (brittle, poor ductility, etc.) Oxygen content is critical for superconductivity Spin singlet pairing d-wave ( = 2) pairing YBa2Cu3O7-d Tl2Ba2CaCu2O8 Two of the most widely-used HTS materials in applications

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