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Seminar: Effects of electron correlations in unconventional multiorbital superconductors






Electron correlations may strongly affect the physics in multiorbital systems. Here I address this issue by studying multiorbital Hubbard models using a U(1) slave spin theory. I present several examples in iron- and nickel-based superconductors to show how orbital-selective correlations influence band structures and topological behaviors in the normal states of these unconventional superconductors. First, I show how orbital selectivity of the energy-level renormalization cooperating with its counterpart in quasiparticle spectral weight causes substantial change to the Fermi surface in LiFeAs. Then, I show the orbital-selective electron correlation effect on the band topology in FeSe0.5Te0.5. It pins the topological gap and surface states very close to the Fermi energy and helps stabilizing the band inversion and Dirac node over a wide interaction parameter range. Finally, I discuss the orbital-selective correlations in the recently discovered bilayer nickel-based superconductor.


Dr. Rong Yu is a professor of physics at Renmin University of China. He received his Ph.D. degree from University of Southern California in 2007. He worked at University of Tennessee, Knoxville and Rice University as a postdoctoral research associate before he joined the faculty at Renmin University in 2013. He has been working on theory of correlated electronic systems. Current research interests include frustration and disorder effects in quantum magnets, correlation effects in unconventional superconductors.