Abstract

Although CDW correlations are a ubiquitous feature of the superconducting cuprates, their disparate properties suggest a crucial role for pinning the CDW to the lattice. Here, we report coherent resonant X-ray speckle correlation analysis, which directly determines the reproducibility of CDW domain patterns in La1.875Ba0.125CuO4 (LBCO 1/8) with thermal cycling. While CDW order is only observed below 54 K, where a structural phase transition creates inequivalent Cu-O bonds, we discover remarkably reproducible CDW domain memory upon repeated cycling to far higher temperatures. That memory is only lost on cycling to 240(3) K, which recovers the four-fold symmetry of the CuO2 planes. We infer that the structural features that develop below 240 K determine the CDW pinning landscape below 54 K. This opens a view into the complex coupling between charge and lattice degrees of freedom in superconducting cuprates.

Highlights

  • charge density wave (CDW) correlations are a ubiquitous feature of the superconducting cuprates, their disparate properties suggest a crucial role for pinning the CDW to the lattice

  • As the main difference between these compounds is a subtle change in the crystal structure[20], it is evident the lattice that hosts the CDW correlations has a dramatic influence on the properties of the CDW and the superconducting ground state

  • While the LTO phase transition is common for both LBCO and LSCO, the LTT structural transition is a special feature in LBCO that coincides with the CDW formation

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Summary

Introduction

CDW correlations are a ubiquitous feature of the superconducting cuprates, their disparate properties suggest a crucial role for pinning the CDW to the lattice. We report coherent resonant X-ray speckle correlation analysis, which directly determines the reproducibility of CDW domain patterns in La1.875Ba0.125CuO4 (LBCO 1/8) with thermal cycling. CDWs have been observed in essentially all hole-doped cuprates, but with distinct transition temperatures, correlation lengths, and wavevectors[4,5,6,7,8,9,10,11] This is epitomized by comparing two very similar cuprates that have slightly different low-temperature crystal structures: La1.875Sr0.125CuO4 (LSCO 1/8) and LBCO 1/8. We discover strikingly reproducible CDW domain formation upon repeated thermal cycling well above its transition temperature and show that the CDW pinning memory is defined by structures that form at the LTO transition at 236(5) K rather than disorder or the LTT transition at 54(1) K that appears alongside CDW order

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