Title: Superconductivity, The Iron Age.
When: 22 November, 2016, 12h30
Where: Sala de Conferencias, Módulo 00, Faculty of Science.
Speaker: Peter Hirschfeld, Department of Physics, University of Florida.
The new iron-based superconductors have occasioned great excitement because transition temperatures are high, and it is hoped that the existence of a second class of such superconductors in addition to cuprates will lead to new insights into the essential ingredients for high temperature superconductivity.
I will review what is known about the superconducting state and explain the basis for the near-consensus that almost all such materials display spin singlet, s-wave pair symmetry, but that the order parameter changes sign over the Fermi surface. The electrons that pair also possess an orbital degree of freedom, which plays an unusual role. Different experimental probes on different materials show a large diversity of superconducting gap structures, with evidence for both gap nodes and fully gapped behavior. Within the context of a spin fluctuation pairing theory of such systems, this unexpected variety of gap structures can be easily understood.
High-Tc superconductivity in these unusual multiband materials poses anew the question of how higher temperature superconductivity might be achieved, and offers some new insights.