Matrix-pairing states in the alkaline Fe-selenide superconductors: exotic Josephson junctions

Emilian M. Nica, Qimiao Si, Onur Erten

True to their unconventional nature, multi-band alkaline Fe-selenides and, more recently, the heavy-fermion CeCu${}_2$Si${}_2$ have shown signatures of fully-gapped but sign-changi…