Topological Flat Minibands and Fractional Chern Insulators in Rashba Systems with Tunable Superlattice Potentials

We propose a programmable platform for engineering topological flat minibands by imposing a tunable electrostatic superlattice potential on a Rashba spin-orbit-coupled thin film subject to a Zeeman field. The interplay between the superlattice potential and Zeeman coupling produces an isolated flat miniband with Chern number $\mathcal{C}=1$. Using many-body exact diagonalization, we show that this miniband supports fractional Chern insulators at filling factors $n=1\mathrm{/}3$ and $2\mathrm{/}3$, both of which remain robust over broad parameter ranges. We further identify realistic material candidates and the corresponding device conditions that enable experimental realization. These results establish a versatile and experimentally accessible platform for engineering topological flat minibands and exploring correlated topological phases.