A sign of change: pinning down the pairing symmetry of the iron-based superconductors

TYPECondensed Matter Seminar
Speaker:Erez Berg
Organizer:M. Reznikov
Location:Lidow Nathan Rosen (300)
Remark:Candidate for a faculty position
Abstract:The iron-based superconductors, discovered a couple of years
ago, hold a great promise, from both a technological and a scientific
point of view. With an unusually high maximum critical temperature
exceeding 50K, second only to that of the so-called copper-oxide
high-temperature superconductors, they are likely to belong to a class
of "unconventional" superconductors, whose mechanism lies beyond the
Bardeen-Cooper-Schrieffer theory of phonon-mediated pairing. A crucial
step to unveil the mechanism of superconductivity in these materials
is to understand the structure of their order parameter. In this talk,
I will discuss theoretical investigations of the iron-based
superconductors, which indicate an exotic order
parameter with an internal sign change. Experimentally, detecting such
a sign change poses a significant challenge. I will show how a recent
intriguing experiment, which shows fractional flux quantization in a
composite superconducting loop, can be intepreted as evidence for a
sign-changing order parameter.