Chirality-driven mass enhancement in the kagome Hubbard model.

We investigate the quasiparticle-mass enhancement in the Hubbard model on the frustrated kagome lattice by using a cluster extension of the dynamical mean-field theory. By analyzing the cluster density matrix, we find a hierarchy of energy scale among charge, spin, and chirality degrees of freedom. A large amount of entropy associated with the chirality is released at a much lower temperature than other energy scales for spin and charge fluctuations, leading to a sharp peak in the specific heat and the single-particle spectrum. The results manifest a generic mechanism of mass enhancement driven by an emergent composite degree of freedom under geometrical frustration.