Increase of the critical current by an external electric field in high-temperature superconductors

An electric field directed perpendicular to the surface of a superconductor changes the superconducting properties near the surface and creates an additional barrier for flux penetration into the sample. This effect is characterized by the value ${\mathit{l}}_{\mathit{D}}$/ξ, where ${\mathit{l}}_{\mathit{D}}$ is the Debye screening length and ξ is the coherence length, and can be neglected in conventional superconductors with ${\mathit{l}}_{\mathit{D}}$≪ξ. However, in high-temperature superconductors, where ${\mathit{l}}_{\mathit{D}}$/ξ∼1, the effect is very pronounced and could be used for improvement of the transport critical current.