First-Principles Simulation of Quantized Charge Transport in Extended Systems

北卡罗来纳大学教堂山分校的金井裕介教授获得了化学学部化学理论、模型和计算方法计划以及材料研究部凝聚态物质和材料理论计划颁发的奖项，以研究扩展化学体系中的电子输运。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)并行(同时)执行一组协调计算来模拟电子运动-这被称为大规模并行计算。他们正在使用这项技术来研究电子如何在材料中运动的微观细节，即材料如何携带电流。这项研究可能会使现代电子产品继续缩小尺寸，同时提高速度和复杂性。如果科学家能够利用其独特的导电性，一种名为拓扑材料的新材料代表着改进电子学的巨大机会。目前，对于拓扑绝缘体中的化学特性如何控制独特的电子传输行为，目前还缺乏科学的理解。通过开发新的计算方法，新的模拟将使人们能够从微观上理解电子传输性质是如何在分子水平上受到控制的。研究活动还将促进对计算科学感兴趣的未被充分代表的少数族裔学生在本科水平上的科学教育，金井教授通过暑期实践工作坊吸引学生，在那里学生建造并行计算机并学习硬件和软件开发。学生将被教授在他们建造的计算机上进行电子结构计算和编写简单的代码。大规模的、实时的含时密度泛函理论(TDDFT)方法是在最大局域Wannier函数(MLWF)规范中形成的。它被用来在分子水平上发展对扩展系统中量子化电荷传输的基本理解。通过模拟实际化学体系中的量子力学电子动力学，研究了超越典型绝热演化极限的拓扑Floquet理论。特别是，我们研究了量子化的电荷输运行为，并研究了如何潜在地利用化学部分来控制量子化的输运。这项工作进一步探索了呈现量子化电导的光选通晶体管的新概念。本研究的一个重要方面是通过结合先进的交换相关近似，通过依赖时间的MLWF改进实时TDDFT代码。金井教授还在工作室提供TDDFT方法的实践教程。这一奖项反映了NSF的法定使命，并通过使用基金会的智力优势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.