Physical Properties, Charge Density Waves, and Superconductivity in Ca₃(Rh_xIr_1-x)₄Sn₁₃

The coexistence of charge-density wave ordering (CDW) and superconductivity (SC) was studied in the "3-4-13" stannides, Ca₃(Rh_xIr_1-x)₄Sn_13, using transport and magnetic measurements. Long-range CDW order coexists with superconductivity  up to some concentration between x=0.6 and x=0.7 where the CDW transition terminates at the quantum critical point (QCP). Typically for CDW/SC systems, a short-range CDW still persists beyond critical concentration, maybe even up to x=1. Our earlier report of the effects of electron irradiation in the stoichiometric compounds was extended to alloys in this study, including the QCP composition. A large rate of T_c suppression combined with fully-gapped superconductivity point to unconventional pairing in this system.