Electrically controlled ferromagnetism in 2-dimensional semiconductors

DIMAG项目致力于建立一种新型的二维磁性材料，它不仅表现出一种全新的铁磁行为，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）、固体物理实验室（法国CNRS）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数理论方法，这些方法是实现DIMAG目标的关键，而这些目标又超越了最先进的水平。DIMAG的总体目标是诱导和研究在二维半导体中表现出态密度（DOS）的Van Hove奇点的stoner型铁磁性，正如对GaSe， InSe和SnO的预测。首先，我们将开发具有控制层数的高质量二维材料的合成，通过从商业上可用的单晶中剥离，以及通过分子束外延。我们将优化层数，以最大化Van Hove奇点处的DOS，作为低层数和高层质量之间的折衷。同时，我们将发展范霍夫奇点附近费米能级的控制（通过受体掺杂和电门控），这被预测会导致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学在原子尺度上探测结构、电子和磁性；角度分辨光发射光谱和逆光发射光谱（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射线磁圆二色性和磁光克尔效应建立铁磁行为的内在起源。在此基础上，我们将优化材料的合成，旨在：(1)将有序温度和载流子自旋极化提高到可达到的最高值；（ii）在具有电压偏置的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，即分部1（使能科学和材料），工作包1和2 （WP1 -使能研究；WP2 -自旋电子学）。除了其潜在的基本性质之外，该项目是高度面向应用程序的，因为它旨在提供与设备兼容的新功能。DIMAG将旗舰的WP1和WP2超越石墨烯，进入新的2D材料，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.