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PRODID:UW-Madison-Physics-Events
BEGIN:VEVENT
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UID:UW-Physics-Event-2007
DTSTART:20101213T180000Z
DURATION:PT1H0M0S
DTSTAMP:20240329T052010Z
LAST-MODIFIED:20101129T205536Z
LOCATION:5310 Chamberlin
SUMMARY:Electronic correlations in the optical properties of the iron-
based superconductors\, R. G. Herb Condensed Matter Seminar\, Christop
her Homes\, Brookhaven National Lab
DESCRIPTION:The complex conductivity of the iron-arsenic superconducto
r BaFe1.85Co0.15As2 (Tc â‰
… 25 K) and the iron-chalcogenide superconductor FeTe0.55Se
0.45 (Tc ≅ 14 K) have been determined over a w
ide frequency range for light polarized in the planes at a variety of
temperatures above and below Tc. The optical properties of
the superconducting materials are compared with their metallic parent
compounds\, BaFe2As2 and Fe1.03Te. De
spite being multiband systems\, the low-frequency conductivity in the
electron-doped iron-arsenic material is dominated by a single (electro
n) pocket\, which can be described by a simple Drude model. Not surpri
singly\, the electron-boson coupling constant λ ≅ 1\, indicating th
at this material is not strongly correlated. Below Tc there
is a clear signature of the superconductivity in the optical conducti
vity and there is evidence that more than one energy scale is involved
in the superconductivity. However\, at low temperature (T << Tc<
/sub>) less than 50% of the free carriers have collapsed into the cond
ensate indicating that this material is not in the clean limit [1]. In
contrast\, the low-frequency conductivity of the iron-chalcogenide co
mpounds is non-Drude at low temperature\, with λ ≅ 5 - 7 in the sup
erconducting material\, indicating a much greater degree of electronic
correlation. Below Tc there is once again evidence for two
energy scales in the superconductivity - this may be interpreted as e
ither the isotropic gapping of the electron and hole pockets\, or the
anisotropic gapping of the electron pocket (s+/- model) [2]
. Both the iron-arsenic and the iron-chalcogenide materials fall close
to the universal scaling line for a BCS dirty-limit superconductor in
the weak-coupling limit\, as do the majority of the high-temperature
copper-oxide superconductors.
\n
\n[1] J. J. Tu et al.\, Phys.
Rev. B 82\, 174509 (2010).
\n[2] C. C. Homes et al.\, Phys
. Rev. B 81\, 180508(R) (2010)\; J. Phys. Chem. Solids (in pres
s).
URL:https://www.physics.wisc.edu/events/?id=2007
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