Four-dimensional <i>J</i>-<i>B</i>-<i>T</i>-ε critical surface for superconductors

Abstract

The concept of a superconducting critical surface in a four-dimensional J-B-T-ε space is introduced and from this a critical strain parameter εc is defined in analogy to the usual three superconducting critical parameters: Jc, Bc2, and Tc. Examples of a subset of this surface in a three-dimensional J-B-ε space are presented as a function of temperature for the A15 superconductors, Nb3Sn and V3Ga, utilizing the recently discovered strain scaling law. The usefulness of the J-B-T-ε critical surface in characterizing the interaction of strain with the other three critical parameters and in setting strain limits for the mechanical design of superconducting devices is illustrated.