Ultrafast time-resolved x-ray scattering reveals diffusive charge order dynamics in La<sub>2-<i>x</i></sub> Ba <i><sub>x</sub></i> CuO<sub>4</sub>.
basic_science · Level V
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- Record sourced from PubMed, PMID 31453340.
- Also identified by DOI 10.1126/sciadv.aax3346 and PMC identifier 6697434.
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Abstract
Charge order is universal among high-<i>T</i> <sub>c</sub> cuprates, but its relation to superconductivity is unclear. While static order competes with superconductivity, dynamic order may be favorable and even contribute to Cooper pairing. Using time-resolved resonant soft x-ray scattering at a free-electron laser, we show that the charge order in prototypical La<sub>2-<i>x</i></sub> Ba <i><sub>x</sub></i> CuO<sub>4</sub> exhibits transverse fluctuations at picosecond time scales. These sub-millielectron volt excitations propagate by Brownian-like diffusion and have an energy scale remarkably close to the superconducting <i>T</i> <sub>c</sub>. At sub-millielectron volt energy scales, the dynamics are governed by universal scaling laws defined by the propagation of topological defects. Our results show that charge order in La<sub>2-<i>x</i></sub> Ba <i><sub>x</sub></i> CuO<sub>4</sub> exhibits dynamics favorable to the in-plane superconducting tunneling and establish time-resolved x-rays as a means to study excitations at energy scales inaccessible to conventional scattering techniques.