Structural symmetry breaking and recovery in condensed matter systems are closely related to exotic physical properties such as superconductivity (SC), magnetism, spin density waves (SDW) and charge density waves (CDW). The interplay between different order parameters is intricate and often subject to intense debate, as in the case of CDW order and superconductivity. In La${}_{1.875}$Ba${}_{0.125}$CuO${}_4$ (LBCO), the low-temperature structural domain walls are hypothesized as nanometer scale pinning sites for the CDWs. Coherent X-ray diffraction techniques have been employed here to visualize the domain structures associated with these symmetry changes directly during phase transition. We have pushed Bragg Coherent Diffractive Imaging (BCDI) into the cryogenic regime where most phase transitions in quantum materials reside. Utilizing BCDI, we image the structural evolution of LBCO microcrystal samples during the high-temperature tetragonal (HTT) to low-temperature orthorhombic (LTO) phase transition. Our results show the formation of LTO domains close to the transition temperature and how the domain size decreases with temperature. The number of domains follows the secondary order parameter (or orthorhombic strain) measurement with a critical exponent that is consistent with the 3D universality class.

中文翻译：

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原型高温超导体La1.875Ba0.125CuO4中低温正交晶域的缩放行为

凝聚态系统中结构对称性的破坏和恢复与奇特的物理性质（如超导性（SC），磁性，自旋密度波（SDW）和电荷密度波（CDW））密切相关。与CDW阶和超导性一样，不同阶参数之间的相互作用是复杂的，并且经常引起激烈的争论。在拉${}_{1.875}$巴${}_{0.125}$氧化铜${}_4$（LBCO），低温结构域壁被假定为CDW的纳米级钉扎位点。相干X射线衍射技术已被用于在相变过程中直接可视化与这些对称性变化相关的畴结构。我们已经将布拉格相干衍射成像（BCDI）推入了低温状态，该状态下量子材料中的大多数相变都存在。利用BCDI，我们成像了从高温四方（HTT）到低温正交（LTO）相变期间LBCO微晶样品的结构演变。我们的结果表明，LTO域的形成接近转变温度，并且域大小如何随温度降低。