@article{discovery116271, volume = {98}, month = {February}, publisher = {AMERICAN PHYSICAL SOC}, note = {{\copyright} 2007 The American Physical Society}, number = {6}, journal = {PHYS REV LETT}, year = {2007}, title = {Bulk evidence for single-gap s-wave superconductivity in the intercalated graphite superconductor C6Yb}, issn = {0031-9007}, keywords = {THERMAL-CONDUCTIVITY, FIELD, STATE, MODEL}, author = {Sutherland, M and Doiron-Leyraud, N and Taillefer, L and Weller, T and Ellerby, M and Saxena, SS}, url = {http://dx.doi.org/10.1103/PhysRevLett.98.067003}, abstract = {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 {\ensuremath{<}} H {\ensuremath{<}} 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.} }