Fractionalization and topological point defects in the charge-ordered kagome lattice

The charge-ordered state on the kagome lattice shows some features which are closely related to two-dimensional topological insulators. This motivated us to study a two-dimensional system of spin-polarized fermions on the kagome lattice at filling fraction $f=1/3$ interacting through a nearest-neighbor interaction $V$ using the unrestricted mean-field approach. Above a critical interaction strength $V_c$, a charge-density wave is stabilized. We find that topological point defects in the charge order bind a fractional charge. The value of the bound charge is 1/2 as long as an effective sublattice symmetry is preserved but changes continuously with the strength of the symmetry-breaking field. Moreover, we compute the confinement potential between two fractionally charged defects and argue that the polaron state, formed upon doping the charge-density wave, can be viewed as a bound state of two defects.