Critical currents across grain boundaries in polycrystalline CeCoIn₅

The study of grain boundaries (GB) in superconductors has both fundamental and applied interests. In high temperature cuprate superconductors studies of the critical currents across GBs have provided important information on the symmetry of the order parameter and are critical for the observation of spontaneously generated half-flux magnetic quanta [1]. Similar to cuprate superconductors, heavy fermion superconductors (HFS) host rich physics in the form of unconventional superconducting phases with nodal quasiparticles. However, there have been relatively few phase sensitive measurements of the order parameter thereby emphasizing the need for investigations of critical currents across GBs in HFS.

In this talk, I will present results on GBs in polycrystalline samples of the HFS CeCoIn₅. Electron backscatter diffraction images of well-polished samples reveal that majority of grains are not randomly oriented as one would expect but grow at an angle of 90^o with respect to their neighboring grain. We performed critical current studies on various such GBs. Such investigations across GB are crucial to understand the superconducting order parameter symmetry of CeCoIn₅ and its potential use in devices for quantum information science.

1. H. Hilgenkamp et al., Rev. Mod. Phys. 74, 485, 2002