Hund's metal physics in iron-based superconductors

Tuesday, April 22, 2014 - 3:30pm - 4:45pm
Regents 109
Kristjan Haule
Rutgers University

For more than a century, emergent states of quantum matter such as superconductivity, superfluidity, and quantum magnetism have played a central role in condensed matter and macroscopic quantum physics. We will begin with a review of the history of these discoveries that have had profound impacts on other fields such as elementary particles and astrophysics.

While only copper-based high-Tc (HTC) superconductors were known, the hypothesis that the single-band with strong onsite Hubbard interaction U in proximity to the Mott-insulating state, contains the key to the superconductivity was persuasive. However, the iron-based superconductors, discovered in 2008, showed that HTC superconductivity also occurs in Hunds metals, i.e., multiband systems where the electronic correlations are governed by the Hunds coupling rather than Hubbard U.

In this talk, we will show that the combination of density functional theory and dynamic mean field theory properly incorporates the Hund’s physics as well as realistic band structures, and thereby is well suited to capture and predict a wide range of physical properties and their trends in iron superconductors, such as optical conductivity, x-ray spectroscopy, Fermi surface, magnetic ordering and moments, spin excitations, effective masses, and superconducting pairing symmetry.

REFRESHMENTS AT 3:20 PM IN REGENTS 109

Host: Jim Freericks
Discussion Leader: Wes Mathews