Crystal symmetry of stripe-ordered La1.88Sr0.12CuO4

Abstract

We present a combined x-ray and neutron diffraction study of the stripe-ordered superconductor ${\mathrm{La}}_{1.88}{\mathrm{Sr}}_{0.12}{\mathrm{CuO}}_{4}$. The average crystal structure is consistent with the orthorhombic $Bmab$ space group as commonly reported in the literature. This structure, however, is not symmetry compatible with a second-order phase transition into the stripe order phase, and as we report here, numerous Bragg peaks forbidden in the $Bmab$ space group are observed. We have studied and analyzed these $Bmab$-forbidden Bragg reflections. Fitting of the diffraction intensities yields monoclinic lattice distortions that are symmetry consistent with charge stripe order.