Specific heat of Ca${}_{0.32}$Na${}_{0.68}$Fe${}_2$As${}_2$ single crystals: unconventional s${}_{\pm }$ multi-band superconductivity with intermediate repulsive interband coupling and sizable attractive intraband couplings

S. Johnston, M. Abdel-Hafiez, L. Harnagea +9

We report a low-temperature specific heat study of high-quality single crystals of the heavily hole doped superconductor Ca${}_{0.32}$Na${}_{0.68}$Fe${}_2$As${}_2$. This compound exhibits…