On the origin of the controversial electrostatic field effect in superconductors

Abstract

In semiconductor electronics, the field-effect refers to the control of electrical conductivity in nanoscale devices, which underpins the field-effect transistor, one of the cornerstones of present-day semiconductor technology. The effect is enabled by the penetration of the electric field far into a weakly doped semiconductor, whose charge density is not sufficient to screen the field. On the contrary, the charge density in metals and superconductors is so large that the field decays exponentially from the surface and can penetrate only a short distance into the material. Hence, the field-effect should not exist in such materials. Nonetheless, recent publications have reported observation of the field-effect in superconductors and proximised normal metal nanodevices. The effect was discovered in gated nanoscale superconducting constrictions as a suppression of the critical current under the application of intense electric field and interpreted in terms of an electric-field induced perturbation propagating inside the superconducting film. Here we show that ours, and previously reported observations, governed by the overheating of the constriction, without recourse to novel physics. The origin of the overheating is a leakage current between the gate and the constriction, which perfectly follows the Fowler-Nordheim model of electron field emission from a metal electrode.c`