Electrically controlled ferromagnetism in 2-dimensional semiconductors

DIMAG项目致力于建立一种新型的2D磁性材料，这种材料不仅具有全新的铁磁行为，而且具有自旋电子学应用的最佳特性。这个为期36个月的项目汇集了5个学术实验室：半导体物理实验室（比利时鲁汶大学）、核与辐射物理研究所（比利时鲁汶大学）、汉堡大学物理系（德国）、固体物理学实验室（法国国家科学研究中心）和新戈里察大学量子光学实验室（斯洛文尼亚）。每个小组都带来了高度专业化的专业知识，以及先进的实验和密度泛函理论方法，这些方法是实现DIMAG目标的关键，而DIMAG的目标又超越了最先进的水平。DIMAG的总体目标是诱导和研究2D半导体中的斯通型铁磁性，这些半导体在态密度（DOS）中表现出货车霍韦奇异性，正如对GaSe，InSe和SnO的预测。首先，我们将开发具有受控层数的高质量2D材料的合成，通过从市售单晶剥离以及通过分子束外延。我们将优化层数，以最大限度地提高在货车霍韦奇点的DOS，作为低层数和高层质量之间的妥协。同时，我们将开发控制的费米能级附近的货车霍韦奇异性（受主掺杂和电门控），这是预测在斯通纳不稳定性，并诱导铁磁状态。我们将详细研究这些效应：扫描隧道显微镜和光谱探测结构，电子和磁性的原子尺度;角度分辨光电子能谱和逆光电子能谱（静态和时间分辨），以充分表征费米能级以下和以上的电子结构; X射线磁性圆二色性和磁光克尔效应建立了铁磁行为的内在起源。基于这种详细的理解，我们将优化材料合成，旨在：（i）将有序温度和载流子自旋极化提高到最高可实现的值;（ii）在电压偏置下在铁磁和非铁磁状态之间可逆切换。DIMAG项目直接解决旗舰工作计划的关键目标，即第1部分（使能科学和材料），工作包1和2（WP 1-使能研究; WP 2-自旋电子学）。除了其潜在的基本性质外，该项目还高度面向应用程序，因为它旨在提供与设备兼容的新功能。将旗舰的WP 1和WP 2超越石墨烯，进入新的2D材料，DIMAG将产生巨大的影响，为具有设备兼容特性和功能的新材料的基础和应用研究开辟广阔的新领域。

The DIMAG project is dedicated to establishing a new type of 2D magnetic materials, which not only exhibits a fundamentally new type of ferromagnetic behavior, but also has optimal characteristics for spintronics applications. This 36-month project, brings together 5 academic laboratories: the Laboratory for Semiconductor Physics (KU Leuven, Belgium), the Institute for Nuclear and Radiation Physics (KU Leuven, Belgium), the Physics Department of the Hamburg University (Germany), the Laboratoire de Physique des Solides (CNRS, France), and Laboratory of Quantum Optics of the University of Nova Gorica (Slovenia). Each group brings highly specialized expertise, and advanced experimental and density functional theory methods that are key to achieving the goals of DIMAG, which in turn are beyond the state of the art. The general goal of DIMAG is to induce and study Stoner-type ferromagnetism in 2D semiconductors exhibiting a Van Hove singularity in the density of states (DOS), as predicted for GaSe, InSe, and SnO. First we will develop the synthesis of high-quality 2D materials with a controlled number of layers, by exfoliation from commercially available single crystals, as well as by molecular beam epitaxy. We will optimize the number of layers in order to maximize the DOS at the Van Hove singularity, as a compromise between low number of layers and high layer quality. In parallel, we will develop the control of the Fermi level in the vicinity of the Van Hove singularity (by acceptor doping and electrical gating), which is predicted to result in a Stoner instability and induce a ferromagnetic state. We will study these effects in detail: scanning tunnelling microscopy and spectroscopy to probe structural, electronic and magnetic properties at the atomic scale; angle resolved photoemission spectroscopy and inverse photoemission spectroscopy (static and time-resolved) to fully characterize the electronic structure below and above the Fermi level; X-ray magnetic circular dichroism and magneto-optical Kerr effect to establish the intrinsic origin of the ferromagnetic behavior. Based on this detailed understanding, we will optimize the materials synthesis, aiming to: (i) increase the ordering temperature and the carrier spin-polarization up to the highest achievable values; (ii) reversibly switch between ferromagnetic and non-ferromagnetic states with voltage bias. The DIMAG project directly addresses key goals of the Flagship work program, namely division 1 (Enabling Science and Materials), work packages 1 and 2 (WP1 - Enabling research; WP2 - Spintronics). In addition to its underlying fundamental nature, the project is highly application-oriented, as it aims to deliver new functionality that is device-compatible. Taking the Flagship’s WP1 and WP2 beyond graphene, into new 2D materials, DIMAG will have a tremendous impact, opening a broad new area of fundamental and applied research on new materials with device-compatible properties and functionality.