Crystallization of fractional charges in a strongly interacting quasihelical quantum dot

The ground-state electron density of a one-dimensional spin-orbit coupled quantum dot with a Zeeman term and strong electron interaction is studied at the fractional helical liquid points. We show that at fractional filling factors ?=(2n+1)-1 (with n a non-negative integer), the density oscillates with N0/? peaks. For n>=1, a number of peaks larger than the number of electrons N0 suggests that a crystal of fractional charges ?e (with e the electron charge) occurs. The reported effect is amenable of verification in a dot coupled to a charged atomic force microscope tip.