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The electronic structure of strongly correlated electrons at the surface of transition-metal oxides

过渡金属氧化物表面强相关电子的电子结构

基本信息

批准号：
16540330
负责人：
ISHIDA Hiroshi
金额：
$ 1.28万
依托单位：
Nihon University
依托单位国家：
日本
项目类别：
Grant-in-Aid for Scientific Research (C)
财政年份：
2004
资助国家：
日本
起止时间：
2004 至 2005
项目状态：
已结题

来源：
https://kaken.nii.ac.jp/en/grant/KAKENHI-PROJECT-16540330/
关键词：
transition metal oxide electron correlation strongly correlated electrons density functional theory dynamical mean-field theory quantum Monte Carlo method embedded Green-function FLAPW 動的有効場理論

项目摘要

We have investigated the electronic structure of strongly correlated electrons at the surface of transition-metal oxides by a first principles method within the local density approximation (LDA) plus dynamical mean-field theory (DMFT). In the DMFT calculation, the single Anderson impurity problem was solved using the quantum Monte Carlo technique of Hirsch and Fye. We focused on the (001) surfaces of cubic perovskite SrVO_3 for which photoemission measurements were performed recently.As the surface structure of SrVO_3 is not known, we first considered its ideal cleaved surfaces with both SrO-layer and VO_2-layer terminations. We used the FLAPW total energy code (FLEUR) to determine the relaxations of surface atoms in the normal direction. It was found that the displacements of the O atoms that constitute octahedrons surrounding central V atoms are rather small. For all the structures, we determined the LDA electronic structure of semi-infinite surfaces using the embedded Green function method. Then, the calculated density of states (DOS) projected on the t_<2g> orbitals of an outermost V atom was used as an input to the subsequent DMFT calculations.For the SrO-layer terminated surfaces, the reduced coordination number of outermost V atoms in the normal direction gives rise to a significant narrowing of the LDA DOS for the d_<xz/yz> bands, which leads to stronger correlation features in the calculated surface quasi-particle spectra than in the bulk. In the case of VO2-layer terminated surfaces, the lack of the local octahedral symmetry at outermost V sites causes substantial changes in the valence electronic structure of the V atoms and results in a considerable rearrangement of t_<2g> valence charge compared to the bulk. This charge transfer among the three t_<2g> orbitals is further promoted by correlation effects.

我们通过局域密度近似 (LDA) 和动态平均场理论 (DMFT) 内的第一原理方法研究了过渡金属氧化物表面强相关电子的电子结构。在DMFT计算中，利用Hirsch和Fye的量子蒙特卡罗技术解决了单个Anderson杂质问题。我们最近对立方钙钛矿SrVO_3的(001)表面进行了光电发射测量。由于SrVO_3的表面结构未知，我们首先考虑其具有SrO层和VO_2层终端的理想解理表面。我们使用 FLAPW 总能量代码 (FLEUR) 来确定表面原子在法线方向上的弛豫。结果发现，构成围绕中心V原子的八面体的O原子的位移相当小。对于所有结构，我们使用嵌入式格林函数方法确定了半无限表面的LDA电子结构。然后，计算出的态密度（DOS）投影在最外层V原子的t_<2g>轨道上，作为后续DMFT计算的输入。对于SrO层终止表面，最外层V原子在法线方向上配位数的减少导致d_<xz/yz>带的LDA DOS显着变窄，从而导致更强的相关特征在计算的表面准粒子光谱中比在本体中。在VO2层终止表面的情况下，最外层V位点缺乏局部八面体对称性导致V原子的价电子结构发生显着变化，并导致与本体相比t_<2g>价电荷的显着重排。相关效应进一步促进了三个t_ 2g 轨道之间的电荷转移。