Absence of backscattering at integrable impurities in one-dimensional quantum many-body systems

We study interacting one-dimensional (1D) quantum lattice gases with integrable impurities. These model Hamiltonians can be derived using the quantum inverse scattering method for inhomogeneous models and are by construction integrable. The absence of backscattering at the impurities is shown to be the characteristic feature of these disordered systems. The value of the effective carrier charge and the Sutherland-Shastry relation are derived for the half-filled XXX model and are shown to be independent of the impurity concentration and strength. For the half-filled XXZ model we show that there is no enhancement of the persistent currents for repulsive interactions. For attractive interactions we identify a crossover regime beyond which enhancement of the currents is observed.