标题： 单层3d过渡金属氧化物 $\mathrm{Sr_2CoO_4}$ 中Hund$'s$ 金属物理的特征 显示英文标题

标题： Signatures of Hund$'s$ metal physics in single-layered 3d transition metal oxide, $\mathrm{Sr_2CoO_4}$

摘要： 利用密度泛函理论和动态平均场理论，我们研究了亨特耦合对$\mathrm{Sr_2CoO_4}$中电子关联性质的影响。 我们的研究结果表明，该化合物具有强烈的亨特金属物理特征。 Co 3$d$态在关联程度和质量增强方面表现出很大的轨道分化。 虚时间关联函数表明系统中存在自旋轨道分离和较大的局部电荷涨落。 在计算的最低温度下，对于各种强度的亨特耦合，都观察到费米-液体图像的崩溃，这表明费米-液体相干性尺度低于$\sim$100 K。有趣的是，在$\sim$200 K，即费米能级附近，其态密度谱中$e_g$轨道突然出现了带隙态。 在Co3$d$态中，3$d_{z^2}$和3$d_{x^2-y^2}$促进了增强的相关性。 本研究明确地确定$\mathrm{Sr_2CoO_4}$是第一种被分类为 Hund 金属的单层3$d$过渡金属氧化物。 显示英文摘要

摘要： With density functional theory plus dynamical mean-field theory, we study the influence of Hund's coupling on the nature of electronic correlations in $\mathrm{Sr_2CoO_4}$. Our results suggest strong signatures of Hund's metal physics in this compound. The Co 3$d$ states show large orbital differentiation in the degree of correlations and mass enhancement. The imaginary-time correlation functions suggest the presence of spin-orbital separation and large local charge fluctuations in the system. Breakdown of the Fermi-liquid picture is observed at the lowest calculated temperature for various strengths of Hund's coupling, suggesting the Fermi-liquid coherence scale lower than $\sim$100 K. Interestingly, a sudden emergence of a gapped state is noted for $e_g$ orbitals in its spectral density of states at $\sim$200 K in the vicinity of Fermi-level. Among the Co 3$d$ states 3$d_{z^2}$ and 3$d_{x^2-y^2}$ foster enlarged correlations. This study conclusively identifies $\mathrm{Sr_2CoO_4}$ as the first single-layered 3$d$ transition metal oxide to be classified as Hund's metal.