Ultrafast helicity-dependent all-optical switching in hybrid magnetic nanomaterials

混合磁性纳米材料中的超快螺旋依赖全光开关

• 批准号: EP/V048538/1
• 负责人: Robert Hicken
• 金额: $ 25.78万
• 依托单位: UNIVERSITY OF EXETER
• 依托单位国家: 英国
• 项目类别: Research Grant
• 财政年份: 2021
• 资助国家: 英国
• 起止时间: 2021 至 无数据
• 项目状态: 已结题
• 来源: https://gtr.ukri.org/projects?ref=EP%2FV048538%2F1
• 关键词: Ultrafast; helicity; dependent; optical; switching

Information technology has transformed our lives, connecting us and providing access to knowledge that was previously the preserve of experts and scholars. And yet today's technology is only a beginning. Embedding information gathering and remote control of objects that we either use or wear will lead to an Internet of Things that greatly extends the amount of information that we need to process and store. For this vision to be realised, the capabilities of the underlying hardware must continue to advance at breakneck speed. The principal focus of this project is on how we might store information in future.Today we are increasingly dependent upon cloud computing that stores and retrieves information from data centres that contain enormous arrays of magnetic hard disk drives (HDDs). We have become accustomed to the idea that the capacity of each HDD will increase every year so that increased demand for storage capacity can be met by regularly replacing each HDD. However, the success of this strategy is now uncertain because the continued miniaturisation of technology needed to increase capacity has reached physical limits that are not easily overcome. Specifically, the size of the region on the surface of a disk that is used to store one "bit" of information (1 or 0), has become so small as to be unstable on the timescale of 10 years that is the industrial standard for date retention. Materials with enhanced stability have been developed, but it is not possible to switch their magnetization, i.e. write data, with the magnetic field available from a conventional magnetic recording head. This has generated intense interest in new mechanisms for magnetic switching that can bypass this seemingly unavoidable bottleneck.This project will explore how light may be used to switch the magnetization of new magnetic materials in which the electronic and magnetic properties can be tailored to optical control. In 2004 it was shown that atomic monolayers of graphene can be peeled from a crystal of graphite, a form of carbon, by a technique known as mechanical exfoliation. The technique is effective because graphene layers are only weakly bonded to their neighbours by what are known as van der Waals forces. In fact, there are many other crystals with similar bonding from which few and monolayer films may be exfoliated. By exfoliating layers from different crystals and stacking them to form a multilayer, it is possible to create hitherto unknown hybrid materials that can combine the favourable properties of their parent crystals. Furthermore, the interface between successive layers can be extremely clean and well ordered. Here the aim is to combine 2 dimensional ferromagnetic (2dFM) layers that have permanent magnetic order with semiconducting transition metal dichalcogenide (TMDC) layers in which electrons can be optically excited with very high efficiency. Furthermore, it is possible to excite electrons that have a magnetic moment, which is associated with their quantum mechanical "spin", with direction determined by the polarization of the incident light.Experiments will be performed in which an ultrafast laser pulse with duration less than 1 trillionth of a second is used to excite electrons in the TMDC layer so that their magnetic moments can interact with the magnetic moments in the 2dFM layer. By controlling the direction of the excited magnetic moments through the polarization of the light, the aim is to switch the magnetization of the 2dFM backwards and forwards at will. Furthermore, the manner and timescales on which the magnetization changes will be determined by using a second laser pulse to interrogate the instantaneous magnetic state at a time of our choosing. While the initial goal is to observe and understand the mechanism of all-optical switching, the ability to combine many different materials will facilitate the search for the combinations that are best suited to data storage applications.

信息技术改变了我们的生活，将我们联系在一起，并提供了获取知识的机会，而这些知识以前是专家和学者的专利。然而，今天的技术只是一个开始。嵌入信息收集和远程控制我们使用或佩戴的对象将导致物联网，大大扩展我们需要处理和存储的信息量。为了实现这一愿景，底层硬件的能力必须继续以惊人的速度发展。这个项目的主要重点是我们未来如何存储信息。今天，我们越来越依赖云计算，云计算存储和检索包含大量硬盘驱动器（HDD）阵列的数据中心的信息。我们已经习惯了这样的想法，即每个HDD的容量每年都会增加，因此通过定期更换每个HDD可以满足对存储容量的增加需求。然而，这一战略的成功现在是不确定的，因为增加产能所需的技术的持续升级已经达到了不容易克服的物理极限。具体地说，用于存储一个“比特”信息（1或0）的磁盘表面区域的大小已经变得如此之小，以至于在10年的时间尺度上不稳定，这是日期保留的工业标准。已经开发了具有增强的稳定性的材料，但是不可能利用从常规磁记录头可获得的磁场来切换它们的磁化，即写入数据。这引起了人们对磁开关新机制的浓厚兴趣，这种机制可以绕过这一看似不可避免的瓶颈。本项目将探索如何利用光来切换新磁性材料的磁化，其中电子和磁性可以根据光学控制进行调整。在2004年，有研究表明，石墨烯的原子单层可以通过一种称为机械剥离的技术从石墨晶体（一种碳的形式）上剥离下来。该技术之所以有效，是因为石墨烯层仅通过所谓的货车德瓦尔斯力与其相邻层弱结合。事实上，有许多其他晶体具有类似的键合，很少和单层膜可以剥离。通过从不同晶体剥离层并将它们堆叠以形成多层，可以产生迄今未知的混合材料，其可以联合收割机结合其母体晶体的有利性质。此外，连续层之间的界面可以非常干净且有序。这里的目的是将具有永磁有序的联合收割机二维铁磁（2dFM）层与半导体过渡金属二硫属化物（TMDC）层组合，在TMDC层中电子可以非常高的效率被光学激发。此外，有可能激发具有磁矩的电子，磁矩与它们的量子力学“自旋”有关，实验中，使用持续时间小于1万亿分之一秒的超快激光脉冲来激发TMDC层中的电子，使得它们的磁矩可以与TMDC层中的磁矩相互作用。2dFM层。通过光的偏振控制激发磁矩的方向，目的是随意前后切换2dFM的磁化。此外，磁化强度变化的方式和时间尺度将通过使用第二激光脉冲在我们选择的时间询问瞬时磁状态来确定。虽然最初的目标是观察和理解全光开关的机制，但联合收割机能够将许多不同的材料结合起来，这将有助于寻找最适合数据存储应用的组合。

项目成果

Laser-induced topological spin switching in a 2D van der Waals magnet.

• DOI: 10.1038/s41467-023-37082-y
• 发表时间: 2023-03-13
• 期刊: NATURE COMMUNICATIONS
• 影响因子: 16.6
• 作者: Khela, Maya;Dabrowski, Maciej;Khan, Safe;Keatley, Paul S.;Verzhbitskiy, Ivan;Eda, Goki;Hicken, Robert J.;Kurebayashi, Hidekazu;Santos, Elton J. G.
• 通讯作者: Santos, Elton J. G.

All-optical control of spin in a 2D van der Waals magnet.

• DOI: 10.1038/s41467-022-33343-4
• 发表时间: 2022-10-10
• 期刊: Nature communications
• 影响因子: 16.6

Laser-induced topological spin switching in a 2D van der Waals magnet

二维范德华磁体中激光诱导的拓扑自旋切换

• DOI: 10.48550/arxiv.2302.06964
• 发表时间: 2023
• 作者: Khela M