CDS&E: Numerical Investigation of Two-Particle Response Functions of Correlated Materials

点击翻译按钮获取中文摘要

NONTECHNICAL SUMMARYThe Division of Materials Research and the Division of Advanced Cyberinfrastructure jointly fund this award, which supports theoretical and computational research aimed at understanding the relationship between experimental measurements and numerical simulations of materials in which strong electronic correlation effects are important. In particular, the team will focus on obtaining computational data simulating a variety of experiments such as nuclear magnetic resonance, neutron spectroscopy, and resonant inelastic x-ray scattering. Materials consist of electrons and ions arranged in a crystal lattice. In some materials, the motion of an electron is strongly interdependent on, or correlated with, the motion of many other electrons. As a consequence, these materials may exhibit unusual behavior including superconductivity, magnetism, and interesting electrical and optical properties. While these properties make them useful and interesting for technical applications, our standard theoretical tools for describing such materials are inadequate, and numerical methods are needed. The subject of this project is the development and application of accurate and controlled numerical methods that can describe correlated electron systems and compute experimentally measured quantities.The project will contribute to broader impacts by supporting the development and maintenance of sustainable open-source community software libraries, which will accelerate the development of future codes as well as provide reliable and state-of-the-art applications to the science community. The software libraries currently maintained by the PI are among the few established open-source libraries for calculations on strongly correlated systems. As part of the project, graduate students will be trained in modern theoretical techniques and in scientific software development.TECHNICAL SUMMARYThe Division of Materials Research and the Division of Advanced Cyberinfrastructure jointly fund this award, which supports theoretical and computational research aimed at understanding the relation between experimentally measured two-particle response functions and generalized susceptibilities of effective low-energy lattice models in systems where strong correlations are important. The project will combine newly developed numerical methods with large-scale calculations to compute the response functions of nuclear magnetic resonance (NMR), neutron spectroscopy, and resonant inelastic x-ray spectroscopy (RIXS) and will investigate the extent to which observed signals can be attributed to electron correlation effects. Susceptibilities reveal important information about collective excitations of a system and are directly measurable in experiment. However, the strong correlation physics of generalized susceptibilities measured by two-particle probes such as NMR, RIXS, or neutron scattering is theoretically not well understood. As a consequence, several contradictions in the interpretation of experimental results exist. This project will build on methods that have shown to be reliable for single-particle excitations that are measured in photoemission and scanning tunneling microscopy, and extend them to investigate two-particle correlation functions. By providing reliable results for the susceptibilities of fermionic lattice models and by computing response functions, this work will facilitate the separation of true electron correlation physics from model-dependent artifacts, which in turn will aid in the interpretation of experiments. Correlated electron materials are essential for modern technological applications such as information technology, energy technology, materials science, and nanoscience. By clarifying the basic behavior of susceptibilities and their relation to experimental work, this project will contribute to our understanding of correlated materials and their characterization. The project will contribute to broader impacts by supporting the development and maintenance of sustainable open-source community software libraries, which will accelerate the development of future codes as well as provide reliable and state-of-the-art applications to the science community. The software libraries currently maintained by the PI are among the few established open-source libraries for calculations on strongly correlated systems. As part of the project, graduate students will be trained in modern theoretical techniques and scientific software development.