Thermal Conductivity of Superconducting (TMTSF)2ClO4: Evidence for a Nodeless Gap

We report on the first measurements of thermal conductivity in the superconducting state of (TMTSF)2ClO4. The electronic contribution to heat transport is found to decrease rapidly below Tc, indicating the absence of low-energy electronic excitations. We argue that this result provides strong evidence for a nodeless superconducting gap function, but does not exclude a possible unconventional order parameter. copyright 1997 The American Physical Society