  The phenomenon of localization usually happens due to the existence of
disorder in a medium. Nevertheless, certain quantum systems allow dynamical
localization solely due to the nature of internal interactions. We study a
discrete time quantum walker which exhibits disorder free localization. The
quantum walker moves on a one-dimensional lattice and interacts with on-site
spins by coherently rotating them around a given axis at each step. Since the
spins do not have dynamics of their own, the system poses the local spin
components along the rotation axis as an extensive number of conserved moments.
When the interaction is weak, the spread of the walker shows subdiffusive
behaviour having downscaled ballistic tails in the evolving probability
distribution at intermediate time scales. However, as the interaction gets
stronger the walker gets exponentially localized in the complete absence of
disorder in both lattice and initial state. Using a matrix-product-state
ansatz, we investigate the relaxation and entanglement dynamics of the on-site
spins due to their coupling with the quantum walker. Surprisingly, we find that
even in the delocalized regime, entanglement growth and relaxation occur slowly
unlike marjority of the other models displaying a localization transition.
