Abstract:     

　　The two-dimensional kagome lattice consisting of corner-sharing triangles possesses unique electronic structures characterized by flat bands, Dirac cones, and van Hove singularities, thereby providing a novel platform to investigate various topological and correlated phenomena. Recently, a new family of nonmagnetic layered kagome metals AV₃Sb₅ (A = K, Rb, and Cs) has attracted enormous attention due to its intriguing electronic properties of nontrivial topological states, chiral charge density wave, and superconductivity. In this talk, I will present our first-principles density-functional theory studies for three different kinds of kagome systems: i.e., ferromagnetic Fe₃Sn₂, antiferromagnetic FeSn, and nonmagnetic CsV₃Sb₅. Our findings demonstrate the presence of a flatband ferromagnetism in Fe₃Sn₂ arising from the highly degenerate and dispersionless manifold state of electrons and the symmetry-protected Dirac fermions in the antiferromagnetic FeSn. I also discuss the origin of the charge density wave, the superconducting pairing mechanism, and the pairing symmetry of superconductivity in CsV₃Sb₅.

About the speaker:

　　Jun-Hyung Cho is currently a Professor in the Physics Dept. at Hanyang University. He received a B.S. degree in Physics Dept. from Hanyang University in 1983, an M.S. degree in theoretical condensed matter physics from Seoul National University in 1986, and a Ph.D. degree in theoretical condensed matter physics from Pohang University of Science and Technology in 1994. He worked as postdoctoral researcher at several different institutions such as Fritz-Haber-institut, Oak Ridge National Laboratory, National Renewable Energy Laboratory, and University of Texas at Austin. In 2003, he joined Hanyang University as Professor.