Reasons of switch-off time decrease in superconductor switches with a buffer layer

摘要

Literature referring to superconductor optoelectronic switches report about curious phenomenon of improvement of dynamical properties as a result of introduction of a thin, low thermal conductivity buffer layer. Present paper is a trial of interpretation of this phenomenon basing on analysis of non-stationary temperature fields within the element's structure. The analysis has been made using the method of numeric modelling of thermal processes occurring within the thin-layer structure consisting of high-temperature superconductor YBa_2Cu_3O_(7-x) sputtered over the MgO substrate and separated with an intermediate SrTiO_3 layer. The essential reason of shortening of key's switch-off time is the fact that the buffer layer limits heat diffusion towards the substrate during switching-on time; as a result its switching-off occurs through heat abstraction towards the high thermal conductivity substrate which temperature is lower than the superconductor's switch-off temperature.