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Where are the superconductors?. Z. Fisk, UC Irvine Digital Synthesis Workshop Boston University September 27, 2013 Supported by AFOSR MURI. (from J. Schilling). timeline of maximum superconducting transition temperature T c. 1986: the new superconductors.
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Where are the superconductors? Z. Fisk, UC Irvine Digital Synthesis Workshop Boston University September 27, 2013 Supported by AFOSR MURI
timeline of maximum superconducting transition temperature Tc
1986: the new superconductors La1.84Sr0.16CuO4 Tc = 40K
the new superconductors: pnictides Tc = 56K Wolfgang Jeitschko 2006 Hirano; 2008 Jorend
What is common here? • all based on electron precise materials • charge separated layers • electronically anisotropic
BCS-type A15 superconductivity • Peierls-type lattice distortion above Tc • strong coupling of soft lattice mode to conduction electrons • no lattice distortion when Tc occurs first
highest Tc found in proximity to competing “localized” phase • holds for BCS, heavy Fermions, organics, cuprates and pnictides • the competing phase, afm in heavy Fermions, terminates where it intersects the Tcboundary and does not extend into the superconducting phase • “localized”: in BCS, lattice distorted; in heavy Fermions, local moment magnetism; in cuprates, the psuedo-gap phase. • electronics highly non-adiabatic • superconductivity runs in structures
superconductivity appears as solution to unloading entropy of fluctuations • gaps out lower frequency fluctuations • It seems plausible that a connection between structure, character of fluctuations and superconductivity exists