Spin-resolved spectro-microscopy of correlated surface and interface systems

相关表面和界面系统的自旋分辨光谱显微镜

• 批准号: 229223408
• 负责人: Professor Dr. Matthias Bode
• 金额: --
• 依托单位: Lehrstuhl für Experimentelle Physik II
• 依托单位国家: 德国
• 项目类别: Research Units
• 财政年份: 2013
• 资助国家: 德国
• 起止时间: 2012-12-31 至 2015-12-31
• 项目状态: 已结题
• 来源: https://gepris.dfg.de/gepris/projekt/229223408?language=en
• 关键词: Spin; resolved; spectro; microscopy; correlated

In this project we will perform spin-averaged and spin-resolved studies of two classes of low- dimensional materials which both exhibit electron correlations, i.e. oxide heterostructures and two-dimensional Kondo lattices. To achieve access to the buried interfaces of oxide heterostructures, such as LaAlO3/SrTiO3 (LAO/STO) or LaVO3/SrTiO3 (LVO/STO), samples will be fractured under UHV conditions to expose their cross-section. Thereby structural and electronic properties of the interfaces can be studied in situ. Combining the atomic resolution capability of scanning tunneling microscopy (STM) with spin-averaging and spin-resolved scanning tunneling spectroscopy (STS) the lateral distribution of the (spin dependent) density of states will be investigated. As far as single layers are concerned key questions to be answered are the position and spatial distribution of the 2-dimensional electron gas. These properties are of particular relevance in multilayer structures where the coupling between the interfaces depends on the periodicity of the layers.We will study the impact of imperfections, such as defects and variations in layers thickness. The results will be compared with photoemission electron microscopy (P4), XMCD-PEEM (P7), and dynamic mean field theory (DMFT) calculations (P8). In the second part of this project we will investigate two-dimensional Kondo systems, such as CePt alloys which are also the subject of projects P3, P7, and P9. While spatially averaging techniques require homogeneous surfaces, the high spatial resolution of STS also allows for the characterization of inhomogeneous surfaces with different local Ce coverages.We will perform high-resolution variable temperature STS above and below the coherence temperature T* which marks the transition between the single impurity limit and coherent heavy-fermion bands. In addition, we will perform spectroscopic imaging (SI) measurements to potentially detect quasi-particle interference (QPI) patterns through Fourier transformation in k-space. Although STS lacks intrinsic k-resolution, it is complementary to other spectroscopic techniques as it offers high-energy resolution above and below the Fermi level for a wide temperature range with the option of applying high magnetic fields.

在这个项目中，我们将进行两类低维材料的自旋平均和自旋分解研究，这两类材料都表现出电子相关性，即氧化物异质结构和二维近藤晶格。为了获得氧化异质结构的埋藏界面，如LaAlO3/SrTiO3 （LAO/STO）或LaVO3/SrTiO3 (LVO/STO)，将在特高压条件下破裂样品以暴露其横截面。从而可以原位研究界面的结构和电子特性。将扫描隧道显微镜（STM）的原子分辨能力与自旋平均和自旋分辨扫描隧道光谱（STS）相结合，研究了（自旋依赖的）态密度的横向分布。就单层而言，需要回答的关键问题是二维电子气体的位置和空间分布。这些性质在多层结构中具有特别的相关性，其中界面之间的耦合取决于层的周期性。我们将研究缺陷的影响，如缺陷和层厚度的变化。结果将与光电电子显微镜（P4）、XMCD-PEEM （P7）和动态平均场理论（DMFT）计算（P8）进行比较。在这个项目的第二部分，我们将研究二维近藤系统，如CePt合金，这也是项目P3， P7和P9的主题。虽然空间平均技术需要均匀表面，但STS的高空间分辨率也允许表征具有不同局部Ce覆盖率的非均匀表面。我们将在相干温度T*上下进行高分辨率变温STS，这标志着单杂质极限和相干重费米子带之间的转变。此外，我们将进行光谱成像（SI）测量，以通过k空间中的傅里叶变换潜在地检测准粒子干涉（QPI）模式。虽然STS缺乏固有的k分辨率，但它是其他光谱技术的补充，因为它可以在宽温度范围内提供高于或低于费米能级的高能分辨率，并可选择施加高磁场。