First-Principles Simulation of Quantized Charge Transport in Extended Systems

北卡罗莱纳大学教堂山分校的Yosuke Kanai教授获得了化学系化学理论、模型和计算方法项目以及材料研究部凝聚态物质和材料理论项目的奖励，以研究扩展化学系统中的电子传输。他的研究推进了计算方法，并利用大量处理器（或单独的计算机）模拟电子运动，以并行（同时）执行一组协调计算——这被称为大规模并行计算。他们正在利用这项技术研究电子在材料中如何运动的微观细节，即材料如何携带电流。这项研究可能使现代电子产品继续缩小尺寸，同时提高速度和复杂性。一种被称为拓扑材料的新材料，如果科学家能够利用其独特的导电性，将为改进电子学带来巨大的机会。目前对拓扑绝缘体中的化学特征如何控制独特的电子传递行为的科学理解在很大程度上是缺乏的。通过开发新的计算方法，新的模拟将使微观理解如何在分子尺度上控制电子传递性质。研究活动还将促进对计算科学感兴趣的少数族裔学生的本科科学教育，Kanai教授通过夏季动手研讨会让学生建立并行计算机并学习硬件和软件开发。学生将被教导进行电子结构计算，并在他们建造的计算机上编写简单的代码。在最大局部化万尼尔函数（MLWF）规范中，建立了大尺度、实时时变密度泛函理论（TDDFT）方法。它用于在分子水平上发展对扩展系统中量子化电荷输运的基本理解。通过模拟实际化学系统中的量子力学电子动力学，研究了拓扑Floquet理论在典型绝热演化极限之外的问题。特别是，研究了量子化电荷输运行为，并研究了如何利用化学成分来控制量子化电荷输运。这项工作进一步探索了具有量子化电导的光门控晶体管的新概念。本研究的一个重要方面是通过时间相关的mlwf结合高级交换相关近似来改进实时TDDFT代码。Kanai教授还在研讨会上提供关于TDDFT方法的实践教程。该奖项反映了美国国家科学基金会的法定使命，并通过使用基金会的知识价值和更广泛的影响审查标准进行评估，被认为值得支持。

Professor Yosuke Kanai of the University of North Carolina at Chapel Hill is supported by an award from the Chemical Theory, Models and Computational Methods Program of the Division of Chemistry and the Condensed Matter and Materials Theory Program of the Division of Materials Research to study the electron transport in extended chemical systems. His research advances computational methodologies and simulates electron motion using of a large number of processors (or separate computers) to perform a set of coordinated computations in parallel (simultaneously) - this is called massively parallel computing. They are using this technique to study microscopic details of how electrons move in materials i.e., how materials carry electrical current. This research may enable modern electronics to continue to decrease in size, while increasing in speed and complexity. A new class of materials called topological materials represents a great opportunity to improve electronics if scientists can exploit their unique electrical conductivity properties. Current scientific understanding of how chemical features in topological insulators control the unique electron transport behavior is largely lacking. By developing novel computational methods, new simulations will enable a microscopic understanding of how electron transport properties are governed at the molecular scale. The research activities will also promote science education at the undergraduate level for underrepresented minority students with interests in computational sciences, Professor Kanai engages students through summer hands-on workshops where the students build a parallel computer and learn about both hardware and software development. The student will be taught to perform electronic structure calculations and program simple code on the computers they build.The large-scale, real-time time-dependent density functional theory (TDDFT) method is formulated in the maximally-localized Wannier function (MLWF) gauge. It is used to develop a fundamental understanding of quantized charge transport in extended systems at the molecular level. Topological Floquet theory is studied beyond the typical adiabatic evolution limit by simulating quantum-mechanical electron dynamics in real chemical systems. In particular, the quantized charge transport behavior is investigated and how chemical moieties can potentially be used to control the quantized transport is studied. The work further explores the novel concept of optically gated transistors that exhibits quantized conductance. Improving the real-time TDDFT code by incorporating advanced exchange-correlation approximations via time-dependent MLWFs is an important aspect of this investigation. Professor Kanai also provides hands-on tutorials on TDDFT methodologies at workshops.This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.