Imaging Domains and Domain Walls in High-Temperature Superconductor*

Phase transition, Symmetry breaking and recovery in condensed matter systems are closely related to the exotic physical properties of strongly correlated materials such as superconductivity, magnetism, ferroelectricity, etc. A key signature of broken symmetry is the formation of structural domains of few nanometer size. Bragg coherent X-ray diffraction techniques can enable novel experimental opportunities to directly visualize symmetry changes in these materials through domain structure. We have pushed Bragg Coherent Diffractive Imaging (BCDI) into the cryogenic regime where most phase transitions in quantum materials reside. Utilizing coherent photons at 34-ID-C beamline of the Advanced Photon Source, we image the structural domain evolution of La_2-xBa_xCuO₄,x=1/8 sample during the low-temperature-orthorhombic (LTO) to high temperature tetragonal (HTT) phase transition. These phases break the local four-fold rotational symmetry of its high temperature tetragonal (HTT) structure and our preliminary data suggests the low-temperature-orthorhombic (LTO) phase is not pinned to local crystal disorder or defects.