Development of Chiral Charge Density Wave Devices

这一建议的目的是扩大我们对手性电荷密度波材料性质的基本理解，并将其应用于新型光电子器件。手性电荷域的操纵将对凝聚态物理产生重大影响，它将为基于集体电子激发的器件打开大门。电子产品使用集中充电系统的主要优点是低功耗、高信息存储密度和高速度。基础研究将包括宏观电学和光学性质表征以及对精心设计的二维材料和器件中手性电荷密度波性质的原子尺度研究。该计划将为学生和青年研究人员提供必要的工具，以在材料科学、凝聚态物理和光电子器件工程领域开展现代基础研究。由于设计的研究活动是高度跨学科的，学生将被鼓励参加跨学科的课程，如纳米科学、电子和扫描探针显微镜以及纳米制造。该计划旨在通过以下方式扩大学生的参与度和鉴赏力：(A)在现有的本科生和研究生水平的纳米科学、纳米电子学和固态物理课程中融入研究元素；(B)培训学生使用最先进的制造和表征工具；以及(C)让学生接触到不同组织的研究企业和合作研究。这项工作将导致培养一名博士生和几名本科生。通过高级论文工作经验和科学研究俱乐部以及S学院的开放参观来接触当地高中是为高中生攻读理工科学位做准备的过度战略的一部分。手性打破了空间反转对称性，导致了意想不到的新电子特性，特别是在降维的系统中。在许多情况下，电子手性是由其产生的系统的特定结构促成的，无论是原子尺度上还是介观尺度上。最近，人们发现宏观关联电子态之一的电荷密度波也表现出手性性质。这一方案探索了利用具有相反手性的纳米尺寸的磁区作为存储和逻辑单元的基本元件的机会。在这一方案中，我们将扩展对手性连续波与飞秒光学微扰和纳秒电流脉冲耦合的动力学本质的基本理解。系统在回到平衡之前所经过的激发亚稳态的动力学可能包括非传统的有序，如铁电、CDW或超导。这些现象的起源是由于存在各种类型的对称性破缺(TiSe2中的对称性反转)，从而引起简并的基态。在低功率电子设备中存在利用这些亚稳态的机会。我们还将优化TiSe2薄膜的生长，以实现高效的器件制造。研究了应变和掺杂对手性CDW热力学的影响。

The goal of this proposal is to extend our fundamental understanding of the properties of chiral charge density wave materials and utilize its properties in new opto-electronic devices. Manipulation of chiral charge domains will be transformative to the condensed matter physics and it will open the doors to devices based on collective electron excitations. The main advantage of using collective charge systems for electronics is lower power dissipation, high density of information storage and high speed. The fundamental studies will involve both macroscopic electronic and optical properties characterization and atomic scale investigations of the chiral charge density wave properties in carefully engineered two-dimensional materials and devices.The program will provide students and young researchers with necessary tools to carry out modern fundamental research in the fields of materials science, condensed matter physics and optoelectronic device engineering. Since the designed research activities are highly interdisciplinary, the students will be stimulated to take classes across disciplines, such as nanoscience, electron and scanning probe microscopy and nanofabrication. The plan is to broaden participation and appreciation of students through (a) incorporating elements of the research in existing nanoscience, nano-electronics and solid-state physics courses at both the undergraduate and graduate level; (b) train students to use state of the art fabrication and characterization tools and (c) expose the students to research enterprise and collaborative research across different organizations.This work should lead to training a PhD student and several undergraduate students. Outreach to local area high schools through senior thesis work experience and science research clubs as well as College' s open houses are part of the overreaching strategy to prepare high school students to pursue science and engineering degrees.Chirality breaks down the spatial inversion symmetry and results in unexpected new electronic properties, in particular in systems with reduced dimensionality. In many cases the electronic chirality is facilitated by the specific structure of the system in which it emerges, either on atomic scale or on mesoscopic scale. Recently, it was discovered that one of the well-studied macroscopically correlated electronic state, the charge density wave, also exhibits chiral properties. This proposal explores the opportunity to use the nanometer-size domains of opposite chirality that are separated with domain walls as basic elements for memory and logic units.In this proposal we will expand the fundamental understanding of the dynamic nature of the coupling of the chiral CDW with femtosecond optical perturbations and nanosecond current pulses. The dynamics of the excited metastable states through which the system traverses before coming back to equilibrium could include unconventional order such as ferroelectricity, CDW or superconductivity. The origin of these phenomena is in the existence of various types of symmetry breaking (inversion symmetry in TiSe2) that gives rise to degenerate ground states. The opportunity exists to exploit these metastable states in low power electronic devices. We will also optimize the growth of TiSe2 thin films in order to enable efficient device fabrication. The effect on strain and doping on chiral CDW thermodynamics will be explored.