Enhanced Drude weight in a one-dimensional system of fermions with pair-hopping events

In one dimension density-density interactions of particles reduce their mobility and hence the Drude weight, which controls the divergence of the optical conductivity at zero frequency, decreases. We study effects of pair-hopping events on this result in a one-dimensional system of spinless fermions. The considered model consists of the usual single-particle hopping and pair-hopping terms. In the absence of the density-density interactions, we first show that a variation of the pair-hopping amplitude results in a monotonic change of the Drude weight. We next demonstrate that weak nearest-neighbor density-density interactions increase the Drude weight, whereas in the regime of strong interactions the Drude weight decreases as expected. Our numerical findings are supported by bosonization results.