Hexagonal CoSn is a newly-discovered frustrated kagome metal. It shows
close-to-textbook flat bands and orbital-selective Dirac fermions, which are
largely associated with its strongly correlated Co-3d orbitals. Because
correlated electronic states are easily regulated by external conditions (such
as chemical doping, pressure, and temperature), the fate of these
kagome-derived electronic bands upon temperature becomes an interesting and
unsolved question. In this work, we try to study the temperature-dependent
electronic structures of hexagonal CoSn by means of the density functional
theory in conjunction with the embedded dynamical mean-field theory. We find
that hexagonal CoSn is in close proximity to a Mott insulating state at ambient
condition. Special attention is devoted to the evolution of its Co-3d
electronic states with respect to temperature. At least six different
temperatures (or energy scales), namely Tβ, TFLβ,
TS1β (and TS2β), TSFβ, and TΛ, are
figured out. They are related to stabilization of the "pseudogap" state,
emergence of the non-Fermi-liquid phase, onset (and completeness) of the
intermediate spin state, occurrence of the spin-frozen phase, beginning of the
orbital freezing transition, respectively.Comment: 8 pages, 5 figure