Download - Where are the superconductors?
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 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
competing order
M. Nicholas et al. Phys. Rev. B 76, 052401 (2007)
generic cuprate phase diagram
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
Batterman and Barrett Phys. Rev. 145, 296 (1966)
Schilling V3Si: TMartensitic / Tc
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