The valence-band spectrum of the ferromagnetic nickel is calculated using the LDA+DMFT method. The auxiliary impurity model emerging in the course of the calculations is discretized and solved with the exact diagonalization, or, more precisely, with the Lanczos method. Particular emphasis is given to spin dependence of the valence-band satellite that is observed around 6 eV below the Fermi level. The calculated satellite is strongly spin polarized in accord with experimental findings.
Calculation of photoemission spectra of the doped Mott insulator La_{1-x}Sr_xTiO_3 using LDA+DMFT(QMC)
采用量子化学从头计算方法LDA+DMFT（QMC）计算了具有强库仑关联的掺杂莫特绝缘体$_{1-x}$ $_{x}$ $_{3}$的光谱性质.它从局域密度近似（LDA）计算的非相互作用电子能带结构出发，引入动力学平均场论（DMFT）的丢失关联，采用数值精确量子Monte-Carlo（QMC）技术求解由此产生的自洽多带单杂质问题。用LDA+DMFT（QMC）方法计算了La $_{1-x}$ Sr $_{x}$ TiO $_{3}$的光电子能谱，计算结果与实验符合得很好，并且在定性和定量上都比标准LDA方法有了很大的改进.
We present a computational study of resonant inelastic x-ray scattering (RIXS) and x-ray absorption in a representative rare-earth nickelate LuNiO$_3$. We study the changes in the spectra across the metal-insulator/site-disproportionation transition. In particular, we address the question of site-selectivity of the two methods in the disproportionated insulating phase and the signature of metal-insulator transition in the fluorescence-like feature of the RIXS spectra. To this end we use the local density approximation + dynamical mean-field theory (LDA+DMFT) approach combined with configuratio…
The LDA+DMFT method is a very powerful tool for gaining insight into the physics of strongly correlated materials. It combines traditional ab-initio density-functional techniques with the dynamical mean-field theory. The core aspects of the method are (i) building material-specific Hubbard-like many-body models and (ii) solving them in the dynamical mean-field approximation. Step (i) requires the construction of a localized one-electron basis, typically a set of Wannier functions. It also involves a number of approximations, such as the choice of the degrees of freedom for which many-body effe…
We present a computational study of $L$-edge resonant inelastic x-ray scattering (RIXS) in correlated 3$d$ transition-metal oxides using an $ab$ $initio$ method based on local density approximation + dynamical mean-field theory (DMFT). The present method, building on Anderson impurity model with an optimized continuum bath within DMFT, is an extension of the cluster model to include unbound electron-hole pair excitations as well as material-specific charge-transfer excitations with less empirical parameters. We find a good agreement with available experimental data. The relationship between co…
We study $1s$ and $2p$ hard x-ray photoemission spectra (XPS) in a series of late transition metal oxides: Fe$_2$O$_3$ (3$d^{5}$), FeTiO$_3$ (3$d^{6}$), CoO (3$d^{7}$) and NiO (3$d^{8}$). The experimental spectra are analyzed with two theoretical approaches: the MO$_6$ cluster model and the local density approximation (LDA) + dynamical mean-field theory (DMFT). Owing to the absence of the core-valence multiplets and spin-orbit coupling, 1$s$ XPS is found to be a sensitive probe of chemical bonding and nonlocal charge-transfer screening, providing complementary information to 2$p$ XPS. The 1$s$…
The LDA+DMFT Approach to Materials with Strong Electronic Correlations
LDA+DMFT是一种新型计算技术，用于具有强关联电子的真实材料（例如过渡金属及其氧化物）的从头算研究。它结合了局域密度近似（LDA）中传统能带结构理论与现代多体方法，动力学平均场理论（DMFT）的优势。在过去的几年中，LDA+DMFT已被证明是一个强大的工具，为现实的建模强相关的电子系统。本文讨论了LDA+DMFT（X）方法的基本思想和建立，其中X是求解DMFT方程的方法。给出了X=QMC（量子蒙特卡罗）和X=NCA（非交叉近似）的计算结果，并进行了比较。通过模型系统La $_{1-x}$ Sr $_{x}$ TiO $_{3}$，我们定性和定量地证明了方法X的重要性。此外，我们还讨论了过渡金属氧化物V $_2$ O $_3$中的Mott-Hubbard金属-绝缘体转变和4f电子系统Ce中的$α$ - $γ$转变的最新结果.
Motivated by recent core-level x-ray photoemission spectroscopy (XPS), x-ray absorption spectroscopy (XAS) and resonant inelastic x-ray scattering (RIXS) experiments for the newly-discovered superconducting infinite-layer nickelate, we investigate the core-level spectra of the parent compounds NdNiO$_2$ and LaNiO$_2$ using the combination of local density approximation and dynamical mean-field theory (LDA+DMFT). Adjusting a charge-transfer energy to match the experimental spectra, we determine the optimal model parameters and discuss the nature of the NdNiO$_2$ ground state. We find that self-…
In the spirit of recently developed LDA+U and LDA+DMFT methods we implement a combination of density functional theory in its local density approximation (LDA) with a $k$- and $ω-$dependent self-energy found from diagrammatic fluctuational exchange (FLEX) approximation. The active Hilbert space here is described by the correlated subset of electrons which allows to tremendously reduce the sizes of matrices needed to represent charge and spin susceptibilities. The method is perturbative in nature but accounts for both bubble and ladder diagrams and accumulates the physics of momentum resolved s…
Approaching finite-temperature phase diagrams of strongly correlated materials: a case study for V2O3
在强关联材料中考察相稳定性和相平衡，需要在局域密度近似（LDA）的多体扩展中达到一个新的水平，而不仅仅是光谱评估。在这里，我们把电荷自洽LDA+动态平均场论（DMFT）的方法的基础上投影局部轨道的LDA+DMFT接口和定制的赝势框架付诸行动，以解决现实的强关联系统的热力学。也就是说，一个著名的原型莫特现象系统V $_2$ O $_3$在较高温度下的电子相图的案例研究。我们能够描述一阶金属到绝缘体的转变与负压和温度的相关总能量的自洽计算与实验结果一致。
Layer-resolved Electronic Structure and Correlation of Low-$n$ Square-planar Nickelates: A DFT+DMFT Prediction of Superconducting Candidates
School of Physics and Key Laboratory of Quantum State Construction and Manipulation (Ministry of Education), Renmin University of China（中国人民大学物理学院和量子态构建与操控教育部重点实验室）；Hefei National Laboratory（合肥国家实验室）
受新合成的混合价尖晶石LiRh $_2$ O $_4$的启发，在230 K以上的金属立方相中观察到大的热电势[Okamoto { \it et al.}（arXiv：0806.2504）]，采用局域密度近似和动力学平均场论相结合的方法（LDA+DMFT）计算了Seebeck系数。实验值不仅被LDA+DMFT很好地再现，而且被较少涉及的玻尔兹曼方程方法。对后者的仔细分析出乎意料地表明，大的热电势的起源与一种非常不同的氧化物有着共同的根源：Na $_x$ CoO $_2$。我们还讨论了如何通过掺杂进一步提高LiRh $_2$ O $_4$的功率因数，这使得该材料在技术应用上更加具有推广价值。
Closing in on possible scenarios for infinite-layer nickelates: comparison of dynamical mean-field theory with angular-resolved photoemission spectroscopy
The debate whether uranium 5f electrons are closer to being localized or itinerant in the ferromagnetic compound UGa2 is not yet fully settled. The experimentally determined magnetic moments are large, approximately 3 Bohr magnetons, suggesting the localized character of the 5f electrons. In the same time, one can identify signs of itinerant as well as localized behavior in various spectroscopic observations. The band theory, employing local exchange-correlation functionals, is biased toward itinerant 5f states and severely underestimates the moments. Using material-specific dynamical mean-fie…
Satellites in core level spectra of photoelectron spectroscopy (PES) can provide crucial information on the electronic structure and chemical bonding in materials, particular in transition metal oxides. This paper explores satellites of the Ti 1$s$ and 2$p$ core level spectra of SrTiO$_3$ and TiO$_2$. Conventionally, soft x-ray PES (SXPS) probes the Ti 2$p$ core level; however, it is not ideal to fully capture satellite features due to its inherent spin-orbit-splitting (SOS). Here, hard x-ray PES(HAXPES) provides access to the Ti 1$s$ spectrum instead, which allows us to study intrinsic charge…
