토토 사이트 순위vestigation of Unconventional Magnetism and Superconductivity by

Discovery of superconductivity in LaFePO in 2006 and LaFeAsO in 2008 opened a new family of superconductors, namely, FeAs or iron-based superconductors. This family of new superconductors has exotic physical properties. They have quasi-two-dimensional electronic structures with multiple Fermi surfaces, and superconductivity appears at the vicinity of antiferromagnetism. Comparison of electronic energy dispersions from the density functional calculations and those from the angle-resolved photoemission spectroscopy shows that electronic energy dispersions are renormalized by many-body effects. Normal-state electronic structures of FeAs superconductors are qualitatively described by standard density functional theory (DFT) while it is claimed that the mass renormalization is quantitatively described by DFT+DMFT. 토토 사이트 순위 ordering is well described by DFT and it is due to local 토토 사이트 순위 moments governed by Heisenberg Hamiltonian rather than spin-density wave due to Fermi-surface nesting. Local 토토 사이트 순위 moments are larger than ordered 토토 사이트 순위 moments, existing even in non토토 사이트 순위 phase. We perform first-principles calculations of electronic and 토토 사이트 순위 properties of FeAs superconductors with various spin configurations to obtain 토토 사이트 순위 exchange couplings of Fe 토토 사이트 순위 moments. We discuss superconducting properties using a modified Eliashberg theory based on material parameters from DFT. This work is supported by the NRF of Korea (Grant No.2011-0018306). Computational resources have been provided by KISTI Supercomputing Center (Project No. KSC-2013-C3-062).