Prediction of magnetic flux-controlled gate voltage in superconducting field-effect transistors

The undirectional model to the superconducting field-effect transistor (SFET) is shown to be thermodynamically unsound. A gate voltage which is controlled by the magnetic flux difference in a Josephson weak link is predicted by energy arguments. For a passive SFET model to be consistent with recent experimental observations of a charge-controlled critical current, a back-reaction from the DC drain-to-source flux (phase difference) to the DC gate voltage is required. As this effect is important in large devices and occurs at V/sub DS/=0, it does not appear to be directly related to charge-space energy bands or quasiparticle interference.<>