  We report on a novel structural Superfluid-Mott Insulator (SF-MI) quantum
phase transition for an interacting one-dimensional Bose gas within permeable
multi-rod lattices, where the rod lengths are varied from zero to the lattice
period length. We use the ab-initio diffusion Monte Carlo method to calculate
the static structure factor, the insulation gap, and the Luttinger parameter,
which we use to determine if the gas is a superfluid or a Mott insulator. For
the Bose gas within a square Kronig-Penney (KP) potential, where barrier and
well widths are equal, the SF-MI coexistence curve shows the same qualitative
and quantitative behavior as that of a typical optical lattice with equal
periodicity but slightly larger height. When we vary the width of the barriers
from zero to the length of the potential period, keeping the height of the KP
barriers, we observe a new way to induce the SF-MI phase transition. Our
results are of significant interest, given the recent progress on the
realization of optical lattices with a subwavelength structure that would
facilitate their experimental observation.
