UC Irvine

We investigated the effect of electron and hole doping on the high-field low-temperature superconducting state in CeCoIn5 by measuring specific heat of CeCo (In1-x Mx) 5 with M=Sn, Cd, and Hg and x up to 0.33% at temperatures down to 0.1 K and fields up to 14 T. Although both Cd and Hg doping (hole doping) suppresses the zero-field Tc monotonically, Hc2 increases with small amounts of doping and has a maximum around x=0.2% (M=Cd). On the other hand, with Sn doping (electron doping) both zero-field Tc and Hc2 decrease monotonically. The critical temperature for the high-field low-temperature superconducting state correlates with Hc2 and Tc, which we interpret in support of the superconducting origin of this state. © 2010 The American Physical Society.