Gap symmetry and Nodal structure of iron-based superconductors

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Date/Time:Thursday, 31 Oct 2013 - Saturday, 02 Nov 2013
Location:PHYSICS Hall Room 3
Channel:Condensed Matter Physics
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Maxim Khodas

Dept. of Physics & Astronomy, Univ. of Iowa

I focus on the paring symmetry in the class of the iron based superconductors with only electron pockets.
According to ARPES and neutron scattering the pairing is neither a d-nor regular s-wave.
Instead a third possibility exists reconciling different observations.
In the theoretical model I'll introduce the special kind of s+- different from that in pnictides is driven by inter-pocket hybridization (scattering by an antiferromagnetic wave-vector)
The competition between the pocket geometry and hybridization is studied within the Ginzburg-Landau phenomenology and gives rise to a rich phase diagram including the s+id phase with broken time reversal symmetry.

Next, I explain why the consistency with neutron scattering is not obvious and how it is reached using the realistic 3D Fermi surfaces.
Finally I compare the predicted Raman peak due to Bardasis-Schrieffer modes with recently observed in-gap excitations in Bg geometry.