title: Nodal to nodeless superconducting energy-gap structure change concomitant with fermi-surface reconstruction in the heavy-fermion compound CeCoIn(5).
abstract: The London penetration depth λ(T) was measured in single crystals of Ce_{1-x}R_{x}CoIn_{5}, R=La, Nd, and Yb down to T_{min}≈50  mK (T_{c}/T_{min}∼50) using a tunnel-diode resonator. In the cleanest samples Δλ(T) is best described by the power law Δλ(T)∝T^{n}, with n∼1, consistent with the existence of line nodes in the superconducting gap. Substitutions of Ce with La, Nd, and Yb lead to similar monotonic suppressions of T_{c}; however, the effects on Δλ(T) differ. While La and Nd substitution leads to an increase in the exponent n and saturation at n∼2, as expected for a dirty nodal superconductor, Yb substitution leads to n>3, suggesting a change from nodal to nodeless superconductivity. This superconducting gap structure change happens in the same doping range where changes of the Fermi-surface topology were reported, implying that the nodal structure and Fermi-surface topology are closely linked.
authors: Ames Laboratory and Department of Physics & Astronomy, Iowa State University, Ames, Iowa 50011, USA.
authors: Hyunsoo
authors: H
authors: Kim
authors: Ames Laboratory and Department of Physics & Astronomy, Iowa State University, Ames, Iowa 50011, USA.
authors: M A
authors: MA
authors: Tanatar
authors: Ames Laboratory and Department of Physics & Astronomy, Iowa State University, Ames, Iowa 50011, USA.
authors: R
authors: R
authors: Flint
authors: Department of Physics, Brookhaven National Laboratory, Upton, New York 11973, USA.
authors: C
authors: C
authors: Petrovic
authors: Department of Physics, Brookhaven National Laboratory, Upton, New York 11973, USA.
authors: Rongwei
authors: R
authors: Hu
authors: Department of Physics, University of California, San Diego, La Jolla, California 92093, USA.
authors: B D
authors: BD
authors: White
authors: Department of Physics, University of California, San Diego, La Jolla, California 92093, USA.
authors: I K
authors: IK
authors: Lum
authors: Department of Physics, University of California, San Diego, La Jolla, California 92093, USA.
authors: M B
authors: MB
authors: Maple
authors: Ames Laboratory and Department of Physics & Astronomy, Iowa State University, Ames, Iowa 50011, USA.
authors: R
authors: R
authors: Prozorov