Recent discovery of iron-based high temperature superconductors has generated intense research activities in the fields of condensed matter physics, materials sciences and physical chemistry.  While only very limited solid understandings have been obtained and more puzzles are being unveiled, it has become clear that this new class of materials is a perfect host for the complex and rich condensed matter physics involving multiple physical effects with similar energy scales.
This talk will start by introducing the general basic questions of condensed matter physics and motivate the research interest in high-temperature superconductivity.  It will then cover the basic idea of density functional theory, followed by the recent intense interest in the new Fe-based high-temperature superconductors.  We will address the electronic and magnetic structure of the iron based superconductors, focusing on effects of the symmetries (and their violations) in the spin, charge, orbital and the translation degree of freedoms.  First, the rich magnetic structure will be discussed in connection with a hidden ferro-orbital order.  Second, the rich variety of magnetic orders found in the families of the parent compounds will be explained using a simple unified picture.  Third, several novel physical effects due to introduced disordered impurities will be discussed.
Ref:
Phys. Rev. Lett. 110, 037001 (2013)
Phys. Rev. Lett. 109, 147003 (2012)
Phys. Rev. B 86, 081106(R) (2012)
Phys. Rev. Lett. 108, 207003 (2012)
Phys. Rev. Lett. 107, 257001 (2011)
Phys. Rev. Lett. 105, 107004 (2010)
Phys. Rev. Lett. 103, 267001 (2009)