Observation of large $h/2e$ and $h/4e$ oscillations in a proximity dc superconducting quantum interference device

摘要

We have measured the magnetoresistance of a dc superconducting quantuminterference device in the form of an interrupted mesoscopic normal-metal loopin contact with two superconducting electrodes. Below the transitiontemperature of the superconducting electrodes, large $h/2e$ periodicmagnetoresistance oscillations are observed. By adding a small dc bias to theac measurement current, $h/4e$ oscillations can be produced. Lowering thetemperature further leads to even larger oscillations, and eventually to sharpswitching from the superconducting state to the normal state. Thisflux-dependent resistance could be utilized to make highly sensitive fluxdetector.