  The parton approach for quantum spin liquids gives a transparent description
of low-energy elementary excitations, e.g., spinons and emergent gauge-field
fluctuations. The latter ones are directly coupled to the hopping/pairing of
spinons. By using the fermionic representation of the $U(1)$ Dirac state on the
kagome lattice and variational Monte Carlo techniques to include the Gutzwiller
projection, we analyse the effect of modifying the gauge fields in the spinon
kinematics. In particular, we construct low-energy monopole excitations, which
are shown to be gapless in the thermodynamic limit. States with a finite number
of monopoles or with a finite density of them are also considered, with
different patterns of the gauge fluxes. We show that these chiral states are
not stabilized in the Heisenberg model with nearest-neighbor super-exchange
couplings, and the Dirac state corresponds to the lowest-energy Ansatz within
this family of variational wave functions. Our results support the idea that
spinons with a gapless conical spectrum coexist with gapless monopole
excitations, even for the spin-1/2 case.
