We present magnetic neutron scattering and specific heat data on the high-${\mathit{T}}_{\mathit{c}}$ superconductor ${\mathrm{La}}_{1.86}$${\mathrm{Sr}}_{0.14}$${\mathrm{CuO}}_4$. Both types of measurements show that even when the samples are superconducting, there are excitations with energies well below 3.5${\mathit{k}}_{\mathit{B}}$${\mathit{T}}_{\mathit{c}}$. These excitations coincide with a magnetic response, χ’’, whose amplitude is considerably below that observed at ${\mathit{T}}_{\mathit{c}}$=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.

• Received 19 April 1993

DOI:https://doi.org/10.1103/PhysRevLett.71.919