Observation of incommensurate magnetic correlations at the lower critical concentration for superconductivity inLa2−xSrxCuO4(x=0.05)

Abstract

Neutron-scattering experiments have been performed on lightly doped ${\mathrm{La}}_{2-x}{\mathrm{Sr}}_x{\mathrm{CuO}}_4$ single crystals in both the insulating $\mathrm{}(x=0.03,0.04,0.05\mathrm{})\mathrm{}$ and superconducting $\mathrm{}(x=0.06\mathrm{})\mathrm{}$ regions. Elastic magnetic peaks are observed at low temperatures in all samples with the maximum peak linewidth occurring at the critical concentration $x_c=\mathrm{0.05.}\mathrm{}$ Incommensurate peaks are observed only at $x=0.05\mathrm{}$, the positions of which are rotated by $45°$ in reciprocal space about $(\pi ,\pi )$ from those observed for $x>~0.06$ in the superconducting phase.