Evolution of the superconducting energy gap structure concomitant with   Fermi surface reconstruction in the heavy-fermion superconductor CeCoIn5
  The London penetration depth, $\lambda (T)$ was measured in single crystals of Ce$_{1-x}R_x$CoIn$_5$, $R$=La, Nd and Yb down to 50~mK ($T_c/T \sim$50) using a tunnel-diode resonator. In the cleanest samples $\Delta \lambda (T)$ is best described by the power law, $\Delta \lambda (T) \propto T^{n}$, with $n \sim 1$, consistent with line nodes. Substitutions of Ce with La, Nd and Yb lead to similar monotonic suppressions of $T_c$, however the effects on $\Delta \lambda(T)$ differ. While La and Nd doping results in an increase of the exponent to $n \sim 2$, as expected for a dirty nodal superconductor, Yb doping leads to $n > 3$, inconsistent with nodes, suggesting a change from nodal to nodeless superconductivity where Fermi surface topology changes were reported, implying that the nodal structure and Fermi surface topology are closely linked. 
Hyunsoo Kim, M. A. Tanatar, R. Flint, C. Petrovic, Rongwei Hu, B. D.   White, I. K. Lum, M. B. Maple, R. Prozorov
cond-mat.supr-con