Manipulation of single spins in ferroelectric oxides from first principles

该奖项支持对可能提供存储或处理信息新方法的材料的研究。在计算机中，信息被编码成一个比特序列，每个比特序列的值可以是0或1。在物理上实现这些位需要一个可以在两种可能的状态之间切换的系统，例如开/关或上/下。存储和处理信息的最小平台之一是电子的量子力学特性，称为“自旋”，它可以有两个可能的值（上/下）。然而，控制这些单自旋是具有挑战性的，因为很难将控制旋钮连接到电子上。本项目将探索含有稀浓度磁掺杂原子的铁电氧化物材料作为实现单自旋控制的系统。铁电体是表现出自发电极化的材料，其方向可以通过施加电场而逆转。当一个孤立的磁掺杂原子插入到铁电体中时，磁掺杂原子的局部空间环境会影响其自旋方向。此外，基于电场的极化反转改变了铁电晶体中的局部空间环境，因此有可能改变自旋的方向。该项目的目标是通过结合量子力学计算机模拟和理论对称性分析，了解如何操纵插入一系列铁电氧化物材料的磁自旋方向。这项科学研究将通过努力增加参与材料科学与工程学科的学生和研究人员的多样性来补充。特别是，通过研究合作，该项目将增加加州大学默塞德分校与劳伦斯伯克利国家实验室之间的学生和科学思想交流。加州大学默塞德分校为大量代表性不足的少数民族学生和/或第一代大学生提供服务。此外，培养博士后研究人员将有助于科学劳动力的发展。该奖项支持对单自旋操纵的理论和计算研究，单自旋是电场存储和处理信息的最小平台之一。该项目将专注于将磁性掺杂原子插入铁电氧化物宿主晶体中，作为实现和探索这一概念的平台。自旋的择优取向通过自旋-轨道相互作用与其局部晶体学环境相联系。在铁电体中，这种局部环境可以通过外加电场下极化开关过程中发生的结构变化来改变，这为电场控制自旋方向提供了一条途径。此外，将铁电体调谐到结构相变附近可能进一步促进电场诱导的自旋取向的突变。结合密度泛函理论计算和群论分析，本项目将推进对一系列钙钛矿和六方氧化铁电体中基于电场的单自旋操纵的基本理解。该项目还将探索插入铁电体拓扑缺陷（如畴壁和涡旋结构）中的单自旋的方向性。这项科学研究将由旨在增加参与材料科学与工程学科的学生和研究人员多样性的活动来补充。这些活动将侧重于增加加州大学默塞德分校与劳伦斯伯克利国家实验室之间的学生和科学思想交流。加州大学默塞德分校为大量未被充分代表的少数民族学生和/或第一代大学生提供服务。此外，作为该项目的一部分，培养一名博士后研究人员将有助于科学劳动力的发展。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。

NONTECHNICAL SUMMARYThis award supports research into materials that may provide new ways to store or process information. In computers, information is encoded in a sequence of bits, each of which can have a value of 0 or 1. Implementing these bits physically requires a system that can be switched between two possible states, such as on/off or up/down. One of the smallest platforms for storing and processing information is a quantum mechanical property of electrons called “spin”, which can take on two possible values (up/down). However, controlling these single spins is challenging, because it is difficult to attach control knobs to electrons.This project will explore ferroelectric oxide materials containing dilute concentrations of magnetic dopant atoms as a system for realizing single spin control. Ferroelectrics are materials that exhibit a spontaneous electrical polarization, the direction of which can be reversed by applying an electric field. When an isolated magnetic dopant atom is inserted into the ferroelectric, the local spatial environment of the magnetic dopant atom impacts the direction of its spin. Furthermore, electric field-based polarization reversal changes the local spatial environment in a ferroelectric crystal, and hence has the potential to modify the spin’s direction. The goal of this project is to understand how to manipulate the direction of magnetic spins inserted into a series of ferroelectric oxide materials by utilizing a combination of quantum mechanical computer simulations and theoretical symmetry analysis.This scientific research will be complemented by efforts to increase the diversity of students and researchers participating in the materials science and engineering discipline. In particular, via research collaborations this project will increase the exchange of students and scientific ideas between the University of California, Merced, which serves a large number of students who are underrepresented minorities and/or first-generation college students, and Lawrence Berkeley National Laboratory. In addition, the training of a postdoctoral researcher will contribute to scientific workforce development.TECHNICAL SUMMARYThis award supports theoretical and computational research on the manipulation of single spins – one of the smallest platforms to store and process information – with electric fields. The project will focus on magnetic dopant atoms inserted into ferroelectric oxide host crystals as a platform to realize and explore this concept. The preferred orientation of a spin is connected to its local crystallographic environment via the spin-orbit interaction. In a ferroelectric, this local environment can be modified by structural changes that occur during polarization switching under applied electric fields, which provides a path towards the electric field control of the spin directionality. In addition, tuning a ferroelectric to near a structural phase transition may further facilitate abrupt electric field-induced changes to spin orientation. Using a combination of density functional theory calculations and group theory analysis, this project will advance fundamental understanding of electric field-based single spin manipulation in a series of perovskite and hexagonal oxide ferroelectrics. The project will also explore the directionality of single spins inserted in topological defects in ferroelectrics, such as domain walls and vortex structures.This scientific research will be complemented by activities geared toward increasing the diversity of students and researchers participating in the materials science and engineering discipline. These activities will focus on increasing the exchange of students and scientific ideas between the University of California, Merced, which serves a large number of students who are underrepresented minorities and/or first-generation college students, and Lawrence Berkeley National Laboratory. In addition, the training of a postdoctoral researcher as a part of this project will contribute to scientific workforce development.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.