We study composite $d$-wave superconductors consisting of randomly oriented and randomly distributed superconducting droplets embedded in a matrix. In a certain range of parameters the application of a small magnetic field enhances the superconductivity in these materials, while larger fields suppress superconductivity as usual in conventional superconductors. We investigate the magnetic field dependence of the superfluid density and the critical temperature of such superconductors.

• Received 5 June 2018
• Revised 25 July 2018

DOI:https://doi.org/10.1103/PhysRevB.98.094508