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
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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