Altered Sr environment inLa2−xSrxCuO4

The atomic arrangement about the Sr atoms in ${\mathrm{La}}_{2-x}{\mathrm{Sr}}_x{\mathrm{CuO}}_4$ was investigated by Sr $K$-edge polarized x-ray-absorption fine structure on oriented powder with $x$=0.075 and 0.1 at $T=20\mathrm{}$ K. Our results confirm that Sr resides at the La lattice site but we discovered it induces major structural distortions in neighboring oxygen atoms. In particular, our best fits indicate that the O(2) apical oxygen to Sr is split into two sites separated by 0.30(4) Å, providing evidence for a strong lattice-hole interaction, i.e., a polaron, which may be involved in the pairing mechanism of these cuprates.