Spontaneous Symmetry Breaking by Charge Stripes in the High Pressure Phase of Superconducting La1:875Ba0:125CuO4

In those cases where charge-stripe order has been observed in cuprates, the crystal structure is such that the average rotational symmetry of the CuO{sub 2} planes is reduced from fourfold to twofold. As a result, one could argue that the reduced lattice symmetry is essential to the existence of stripe order. We use pressure to restore the average fourfold symmetry in a single crystal of La{sub 1.875}Ba{sub 0.125}CuO{sub 4}, and show by x-ray diffraction that charge-stripe order still occurs. Thus, electronically driven stripe order can spontaneously break the lattice symmetry.