  We investigate the topological properties of hardcore bosons possessing
nearest-neighbor repulsive interactions on a two-leg ladder. We show that by
allowing nearest neighbour dimerized interactions instead of hopping
dimerization, the system exhibits topological phases and phase transitions
under proper conditions. First, by assuming uniform hopping throughout the
ladder, we show that when interaction along the legs are dimerized and the
dimerization pattern is different in the legs, a trivial rung-Mott insulator to
a topological bond order phase transition occurs as a function of the
dimerization strength. However, for a fixed dimerization strength, the system
exhibits a topological to trivial phase transition with increase in the rung
hopping. A completely different scenario appears when the rung interaction is
turned on. We obtain that for a ladder with uniform hopping, the repulsive
interaction either turns the topological phase into a trivial rung-Mott
insulator or a charge density wave phase. Such topological features are absent
when the dimerization pattern in the nearest neighbour interaction is
considered to be identical in both the legs of the ladder. We numerically
obtain the ground state properties and also show the signatures of topological
phase transitions through Thouless charge pumping.
