Low energy excitations in superconducting La1.86Sr0.14CuO4

We present magnetic neutron scattering and specific heat data on the high-Tc superconductor La1.86Sr0.14CuO4. Both types of measurements show that even when the samples are superconducting, there are excitations with energies well below 3.5kBTc. These excitations coincide with a magnetic response, χ'', whose amplitude is considerably below that observed at Tc=35±1 K. At the same time, the wave-vector dependence of χ'' is identical to that for the normal state, which implies that the low frequency excitations in our crystals are not those associated with the nodes of a clean d-wave superconductor. However, the data are consistent with gapless superconductivity of the type induced by localized magnetic impurities, clearly observed in the specific heat measurements