Bulk superconductivity at 36 K in ${\mathrm{La}}_{1.8}$${\mathrm{Sr}}_{0.2}$${\mathrm{CuO}}_4$

We report the results of resistivity and magnetic susceptibility measurements in ${\mathrm{La}}_{2\mathrm{-}\mathrm{x}}$ ${\mathrm{Sr}}_{\mathrm{x}}$ ${\mathrm{CuO}}_4$ for x≤0.3. The x=0.2 sample shows a superconducting transition at 36.2 K with a width of 1.4 K. The associated dc diamagnetic susceptibility (Meissner effect) is a large fraction (60%–70%) of the ideal value. We estimate the density of states from critical-field and resistivity data and suggest, by analogy to ${\mathrm{BaPb}}_{1\mathrm{-}\mathrm{x}}$ ${\mathrm{Bi}}_{\mathrm{x}}$ ${\mathrm{O}}_3$, that conventional phonon-mediated superconductivity can account for the high ${\mathrm{T}}_{\mathrm{c}}$ in this class of materials.