近日，清华大学的杨乐仙&杨鲁懿及其研究小组与松山湖材料实验室的郭汉杰等人合作并取得一项新进展。他们揭示了双层和三层镍酸盐超导体关于密度波转变的显著差异性超快动力学。相关研究成果已于2024年10月17日在国际知名学术期刊《科学通报》上发表。

据悉，除了高压高温超导性外，双层和三层镍酸盐超导体La_n+1Ni_nO_3n+1（n=2和3）在常压环境下也展现出许多吸引人的特性，例如轨道依赖的电子关联性、非费米液体行为以及密度波转变。

该研究团队利用超快反射率测量技术，观察到了双层与三层镍酸盐在常压环境下超快动力学的显著差异。在La₄Ni₃O₁₀中，研究人员发现了一种相干声子模式，它涉及La、Ni和O原子的集体振动，而在 La₃Ni₂O₇中则未观察到此模式。

La₄Ni₃O₁₀的弛豫时间在接近密度波转变温度时发生发散，而La₃Ni₂O₇在约150K以上的弛豫时间则与温度成反比，这表明两种化合物的密度波状态存在显著差异，且La₃Ni₂O₇表现出非费米液体行为。

此外，研究人员估算出La₃Ni₂O₇和La₄Ni₃O₁₀的电子-声子耦合常数分别为0.05–0.07和0.12–0.16，这表明电子-声子耦合在La_n+1Ni_nO_3n+1的电子性质中作用相对较小。这项研究不仅揭示了相关的微观相互作用，而且为进一步研究镍酸盐超导体中，超导性与密度波转变之间的相互作用奠定了基础。

附：英文原文

Title: Distinct ultrafast dynamics of bilayer and trilayer nickelate superconductors regarding the density-wave-like transitions

Author: Gang Li d f, Hanjie Guo c, Luyi Yang a h, Lexian Yang a h

Issue&Volume: 2024/10/17

Abstract: In addition to the pressurized high-temperature superconductivity, bilayer and trilayer nickelate superconductors La_n+1Ni_nO_3n+1 (n = 2 and 3) exhibit many intriguing properties at ambient pressure, such as orbital-dependent electronic correlation, non-Fermi liquid behavior, and density-wave transitions. Here, using ultrafast reflectivity measurement, we observe a drastic difference between the ultrafast dynamics of the bilayer and trilayer nickelates at ambient pressure. We observe a coherent phonon mode in La₄Ni₃O₁₀ involving the collective vibration of La, Ni, and O atoms, which is absent in La₃Ni₂O₇. Temperature-dependent relaxation time diverges near the density-wave transition temperature of La₄Ni₃O₁₀, while it is inversely proportional to the temperature in La₃Ni₂O₇ above ～150 K, suggesting a dramatic difference in the density-wave states of the two compounds and a non-Fermi liquid behavior of La₃Ni₂O₇. Moreover, we estimate the electron-phonon coupling constants to be 0.05–0.07 and 0.12–0.16 for La₃Ni₂O₇ and La₄Ni₃O₁₀, respectively, suggesting a relatively minor role of electron-phonon coupling in the electronic properties of La_n+1Ni_nO_3n+1. Our work not only sheds light on the relevant microscopic interaction but also establishes a foundation for further studying the interplay between superconductivity and density-wave transitions in nickelate superconductors.

DOI: 10.1016/j.scib.2024.10.011

Source: https://www.sciencedirect.com/science/article/abs/pii/S2095927324007503