Mott insulators are one of the most
important classes of materials in modern solid-state physics. I will
show that geometrically frustrated Mott insulators can exhibit
unexpected charge effects like spontaneous circular electric currents
that result from certain (scalar) chiral spin orderings or non-uniform
electronic charge distributions associated with a subclass of bond
orderings. We will see how these phases can appear in simple Hubbard
models. In addition, I will show how these low-energy spin states
contribute comparably to the dielectric and magnetic response
functions, leading to interesting phenomena such as dipole-active ESR
transitions, rotation the electric field polarization, and
magneto-electric effects.