  A novel feature for control of carrier mobility is explored in an
order-disorder separated double quantum ring, where the two rings thread
different magnetic fluxes. Here we use simple tight-binding formulation to
describe the system. In our model, the two rings are connected through a single
bond and one of the rings is subjected to impurity, keeping the other ring as
impurity free. In the strong impurity regime, the electron diffusion length
increases with the increase of the impurity strength, while it decreases in the
weak impurity regime. This phenomenon is completely opposite to that of a
conventional disordered double quantum ring, where the electron diffusion
length always decreases with the increase of the disorder strength.
