Superconductors in strong electric fields: Quantum Electrodynamics meets Superconductivity

A static electric field has always been thought to play little role in the physics of ideal conductors, since the screening effects of mobile carriers prevent it from penetrating deep into the bulk of a metal. Very recently however, experimental evidence has been obtained which indicates that static electric fields can be used to manipulate the superconductive properties of metallic BCS superconducting thin films, weakening the critical current. In this paper I will show how possible explanations to this striking effect can be found relying on the analogy between Superconductivity and Quantum Electrodynamics noticed by Nambu and Iona-Lasinio in the sixties. I will show that, following this parallelism, it is possible to predict a new phenomenon: the superconducting Schwinger effect. Secondly I will explain how this new microscopic effect can be connected to a modified Gizburg-Landau theory where additional couplings between electric field and the superconductive condensate are taken into account. Eventually I will connect these theoretical predictions to the experiments, proposing them as a possible explanation of the weakening of superconductivity due to an external electric field.