Fractional periodic persistent current in a twisted normal metal loop: an exact result

We explore a novel mechanism for control of periodicity in persistent current in a twisted normal metal loop threaded by a magnetic flux $\phi$. A simple tight-binding model is used to describe the system. Quite interestingly we see that, depending on the number of twist $p$, the persistent current exhibits $\phi_0/p$ ($\phi_0=ch/e$, the elementary flux-quantum) periodicity. Such fractional periodicity provides a new finding in the study of persistent current.