CAREER: Electronic and Optical Properties in Generalized Moire Systems from First Principles

非技术性总结该职业奖支持理论和计算研究、软件开发以及新型材料的教育工作，这些材料可以通过结合几层（通常为两到四层）原子级薄材料来创建。这种层状材料家族在电子、光学和量子信息应用中表现出了巨大的前景。它们的性质敏感地取决于各层的化学成分、各层之间的相对扭转角，甚至取决于附近支撑材料的存在。因此，这种具有独特性质的分层系统的巨大组合提供了一个尚未开发的科学和工程机会。PI将使用新的理论方法和大规模原子模拟工具的组合来绘制分层系统的大相空间。该奖项将开发的方法不仅将加快模拟速度，还将为如何实现具有所需量子特性的系统提供概念指导。PI将研究一些选定的材料，这些材料可能具有非传统的电子和光学特性。该奖项还将协同社区大学生，以扩大在科学，技术，工程和数学（STEM）领域中代表性不足的少数民族的参与。最后，研究成果还将为拟议的研究生课程提供信息，该课程将向材料科学家和工程师介绍2D和量子材料的概念。这些努力将使层状材料领域更容易为更广泛的社区所接受，加快基础和应用材料发现的步伐，并将这些发现转化为工业。技术总结该奖项支持理论和计算研究以及专注于垂直堆叠的原子级薄层状材料的教育工作。该奖项重点关注显示莫尔图案的系统，其波长远大于单个层的晶体周期性。随着2018年在扭曲双层石墨烯中发现超导性，此类系统引起了相当大的兴趣。事实上，人们对堆叠绝缘、半导体、铁电和磁性单分子层越来越感兴趣，并通过仔细控制这些较长波长尺度下的能量景观来设计新的涌现激发。利用大规模的第一性原理计算机计算，PI将开发研究此类材料组合的方法。研究活动分为三个相辅相成的目标。首先，PI将开发使用DFT和第一性原理参数化力场计算来计算复杂多层范德华结构中的有效莫尔势的方法。结果应该允许社区以低计算成本了解大量分层界面中的电子特性。其次，该奖项将支持开发第一原理方法来计算复杂范德华材料中的激子-其中包括不寻常的材料组合或大量的层堆叠。这些将通过基于GW和GW结合Bethe-Salpeter方程（GW-BSE）方法的从头多体微扰理论计算进行，同时采用新方法将莫尔势的影响纳入其中，而无需对大型超晶胞进行大量计算。PI将系统地研究这种多层系统中涌现激子态的相干性和耦合。最后，该奖项将支持研究扭曲的二维材料如何实现不寻常的一维物理，并应用于传感和存储。同时，该奖项还包括多管齐下的教育部分，以接触处于职业生涯不同阶段的学生，特别强调在STEM领域代表性不足的当地西班牙裔/拉丁裔社区。例如，这些努力包括通过微型实习机会指导社区大学学生，以及设计和提供关于量子和2D材料的研究生课程，该奖项反映了NSF的法定使命，并被认为是值得通过使用基金会的智力价值和更广泛的评估来支持的。影响审查标准。

NONTECHNICAL SUMMARYThis CAREER award supports theoretical and computational research, software development, and educational efforts on new classes of materials that can be created by combining a few layers (typically from two to four) of atomically thin materials.This family of layered materials has demonstrated great promise for use in electronic, optical, and quantum information applications. Their properties depend sensitively on the chemical composition of individual layers, the relative twist angle between each layer, and even the presence of nearby supporting materials. Hence, the vast combination of such layered systems that can be engineered with unique properties offers an untapped scientific and engineering opportunity.The PI will use a combination of new theoretical methods and large-scale atomistic simulation tools to chart this large phase space of layered systems. The methods that will be developed in this award will not only speed up simulations, but also give conceptual guidance on how to realize systems with desired quantum properties. The PI will study a few selected materials that can potentially host unconventional electronic and optical properties.The award will also synergistically involve community college students to broaden the participation of underrepresented minorities in science, technology, engineering, and math (STEM) fields. Finally, the research outcomes will also inform a proposed graduate-level course that introduces concepts of 2D and quantum materials to materials scientists and engineers. Such efforts will make the field of layered materials more accessible to a broader community, increase the pace of fundamental and applied materials discoveries, and translation of such discoveries to industry.TECHNICAL SUMMARYThis award supports theoretical and computational studies and educational efforts focused on vertically stacked, atomically thin layered materials. The award focuses on systems that display moiré patterns with a wavelength much larger than that of the crystal periodicity of the individual layers.Such systems received considerable interest with the discovery of superconductivity in twisted bilayer graphene in 2018. Indeed, there has been a growing interest in stacking insulating, semiconducting, ferroelectric, and magnetic monolayers, and engineering novel emergent excitations by carefully controlling the energy landscape at these longer wavelength scales.Utilizing large-scale first-principles computer calculations, the PI will develop methods to study such material combinations. The research activities are structured in three complementary objectives. First, the PI will develop methods to compute effective moiré potentials in complex, multilayer van-der-Waals structures using DFT and first-principles-parametrized force-field calculations. The outcome should allow the community to understand the electronic properties in a vast set of layered interfaces at low computational cost. Second, the award will support the development of first-principles approaches to compute excitons in complex van-der-Waals materials – which either include unusual materials combinations or a large number of layer stacking. These will be carried out by ab initio many-body perturbation theory calculations based on the GW and GW combined with Bethe-Salpeter equation (GW-BSE) approaches, together with new methods to incorporate the effect of the moiré potential without requiring large calculations on large supercells. The PI will systematically study the coherence and coupling of emergent excitonic states in such multilayer systems. Finally, this award will support investigations on how twisted 2D materials can realize unusual 1D physics, with applications in sensing and storage.In parallel, this award includes a multi-pronged educational component to reach out to students at different stages of their careers, with a particular emphasis on the local Hispanic/Latinx community which is underrepresented in STEM fields. These efforts involve, for instance, the mentoring of community college students through mini-internship opportunities, and designing and offering a graduate-level course on quantum and 2D materials, closing a common gap in the traditional educational curriculum of materials science and physics courses.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.