Impact of the electric field on superconductivity in Bose-Einstein Condensation regime

Abstract: In the strong coupling Bose-Einstein Condensation (BEC) regime the superconductors have two characteristic temperatures: $T^*$- onset of fermion pairing and $T_{sc}$- onset of superconductivity, such that $T_{sc}<T^*$. In the present article, we consider time dependent Ginzburg-Landau theory of superconductors with slab geometry and show that applied electric field, in the temperature interval $(T_{sc},T^*)$, Bose condenses the Cooper pairs thereby increasing the superconductor critical temperature $T^E_{sc}>T_{sc}$. Important consequence is the fact that arbitrary temperature within the interval ($T_{sc},T^*$) is a critical temperature of superconductor transition if an appropriate electric field is applied. This means that if we set the temperature of the system within the above mentioned interval and increase the applied electric field the system undergoes an electric field induced transition to superconductor. We also show the existence of critical value of the applied electric field at which $T^*=T^E_{sc}$. This means that although the system is in BEC regime, away from the BCS one, we can apply an electric field that moves the system to a state with $T^E_{sc}=T^*$, characteristic of BCS regime. The results indicate that applied electric field experiments are a suitable tool to identify the BEC regime of the superconductors. The experiment can determine $T^*$ as a temperature below which the electric field Bose condenses the Cooper pairs, while above it the electrons screen the field and it cannot penetrate.