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VERSION:2.0
CALSCALE:GREGORIAN
PRODID:UW-Madison-Physics-Events
BEGIN:VEVENT
SEQUENCE:0
UID:UW-Physics-Event-3118
DTSTART:20131007T213000Z
DURATION:PT1H0M0S
DTSTAMP:20240319T140322Z
LAST-MODIFIED:20131011T191459Z
LOCATION:Chamberin 5310
SUMMARY:Superconductivity at the onset of spin-density-wave order in a
metal\, Condensed Matter Theory Group Seminar\, Yuxuan Wang\, Physic
s Department
DESCRIPTION:We revisit the issue of superconductivity at the quantum-c
ritical point between a 2D paramagnet and a spin-density-wave (SDW) me
tal with ordering momentum (pi\,pi). This problem is highly non-trivia
l because the system at criticality displays a non-Fermi liquid behavi
or and because the effective coupling constant &\;amp\;#955\; for t
he pairing is generally of order one\, even when the actual interactio
n is smaller than fermionic bandwidth. Previous study [M. A. Metlitski
\, S. Sachdev\, Phys.Rev.B 82\, 075128 (2010)]has found that the leadi
ng renormalization of the pairing vertex contains log2\, like in color
superconductivity. We analyze the full gap equation and argue that su
mming up log2 term does not lead to a pairing instability. Yet\, super
conductivity has no threshold\, even if &\;amp\;#955\; is set to be
small: the subleading log terms give rise to BCS-like Tc&\;amp\;#8
733\;e&\;amp\;#8722\;1/&\;amp\;#955\;. We argue that the analogy
with BCS is not accidental as superconductivity at a QCP is a Fermi l
iquid phenomenon -- it comes from fermions which retain Fermi liquid b
ehavior at criticality. We compute Tc for the actual &\;amp\;#955\;
and find consistency with the numerical results.
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URL:https://www.physics.wisc.edu/events/?id=3118
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