%0 Journal Article %@ 0031-9007 %A Sutherland, M %A Doiron-Leyraud, N %A Taillefer, L %A Weller, T %A Ellerby, M %A Saxena, SS %D 2007 %F discovery:116271 %I AMERICAN PHYSICAL SOC %J PHYS REV LETT %K THERMAL-CONDUCTIVITY, FIELD, STATE, MODEL %N 6 %T Bulk evidence for single-gap s-wave superconductivity in the intercalated graphite superconductor C6Yb %U https://discovery.ucl.ac.uk/id/eprint/116271/ %V 98 %X We report measurements of the in-plane electrical resistivity rho and thermal conductivity kappa of the intercalated graphite superconductor C6Yb down to temperatures as low as T-c/100. When a field is applied along the c axis, the residual electronic linear term kappa(0)/T evolves in an exponential manner for H-c1 < H < H-c2/2. This activated behavior is compelling evidence for an s-wave order parameter, and is a strong argument against the possible existence of multigap superconductivity. %Z © 2007 The American Physical Society