Inhomogeneous distribution of stripe domains in La_1.875Ba_0.125CuO₄

Bragg geometry soft resonant X-ray ptychography was used to image the domain structure of the charge-density wave (CDW) “stripes” in the prototypical cuprate high-temperature superconductor, La_1.875Ba_0.125CuO₄. A pinhole was scanned over the domains on resonance at the Cu L₃ edge to produce overlapped coherent diffraction patterns which were used to reconstruct an image of the CDW domains. Clear inhomogeneities are revealed in the domain sizes over a sub-micron length scale, which is attributed to the pinning of the stripes to underlying twin domains in the parent crystal. The result was achieved with the high soft X-ray coherent flux available at 23-ID-2 (National Synchrotron Light Source II) combined with the high stability of the instrument. In the soft x-ray ptychography image, stripe domains are found to be slightly anisotropic in size and are inhomogeneously distributed in space with larger and smaller stripe domains being clustered together. We suggest that this behavior arises because of active nucleation and pinning of the stripe domains at twin domain walls introduced in the crystal lattice when it passes into its lower symmetry low-temperature orthorhombic phase.

1. L. Wu, et al., Inhomogeneous distribution of stripe domains in La_1.875 Ba_0.125CuO₄ (in preparation).