Effective increase of a superconducting critical temperature due to a configurational entropy of impurities

Abstract

We show theoretically that a superconducting critical temperature can be effectively increased in a fine-grained superconductor, where impurities migrate along the grain boundaries. The distribution of impurities affects the spatial profile of the BCS condensate. Thus, BCS condensate acquires entropy equal to the configurational entropy of impurities. In order to employ this entropy into the superconducting phase dynamics, we suggest to use a quasiparticle trap that removes quasiparticle excitations from the superconductor. This makes the concentration of Cooper pairs a dynamic variable of the entropy, and thus influences the Ginzburg-Landau functional of the superconductor effectively reducing the first expansion coefficient or, in other words, increasing the critical temperature.