"Macroscopic character of composite high-temperature superconducting wires"

S. A. Kivelson: B. Spivak; Physical Review B , 11/03/15.

Additional Authors: B. Spivak

Abstract:

The “d-wave” symmetry of the superconducting order in the cuprate high temperature superconductors is a well established fact [J. Tsuei and J. R. Kirtley, Rev. Mod. Phys. 72, 969 (2000) and D. J. Vanharlingen, Rev. Mod. Phys. 67, 515 (1995)], and one which identifies them as “unconventional.” However, in macroscopic contexts—including many potential applications (i.e., superconducting “wires”)—the material is a composite of randomly oriented superconducting grains in a metallic matrix, in which Josephson coupling between grains mediates the onset of long-range phase coherence. [See, e.g., D. C. Larbalestier et al.Nat. Mater. 13, 375 (2014), A. P. Malozemoff, MRS Bull. 36, 601 (2011), and K. Heine et al.Appl. Phys. Lett. 55, 2441 (1989)] Here we analyze the physics at length scales that are large compared to the size of such grains, and in particular the macroscopic character of the long-range order that emerges. While XY-superconducting glass order and macroscopic d-wave superconductivity may be possible, we show that under many circumstances—especially when the d-wave superconducting grains are embedded in a metallic matrix—the most likely order has global s-wave symmetry.