Multiferroicity in skyrmionic materials

最近发现的空位尖晶石GaV4S8(GVS)中同时存在铁电性和非传统的Skyrmionic自旋织构，有望在这些化合物中产生突出的磁电效应。值得注意的是，GVS是迄今为止已知的第一种也是唯一一种可能会被应用到顶级现代应用中的多铁材料，比如天空离子存储器。为了显著推进基本理解，我们建议在这个双边项目中，通过理论和实验之间的协调纳米级方法，阐明GVS及其相关化合物的基本静态和动态行为。更准确地说，我们独特地将局部尺度的实验检查(通过使用各种扫描探针技术和光学光谱学)与多尺度建模策略(即从头算、相场建模等)相结合。布拉格/捷克共和国(理论)和德累斯顿/德国(实验)的两个参与小组为在拟议的双边项目中进行这项研究提供了理想的基础。因此，项目目标有三个：首先，GVS和其他家庭成员如GeV4S8、GaMo4S8、GaV4Se8中的磁电耦合机制需要全面和基本的了解，只有通过我们协调和互补的理论和实验努力才能获得。其次，所有这些化合物都将受到机械应变、电场、磁场和光场等外部刺激，以便有目的地影响这些独特材料中Skyrmionic相的相图；例如，我们预计磁性织构，即摆线/Skyrmion晶格将旋转到能量有利的方向。第三，这些刺激也将允许研究这些材料在局部1纳米长度尺度上的动力学性质。

The recently discovered coexistence of both ferroelectricity and non-conventional skyrmionic spin textures in the lacunar spinel GaV4S8 (GVS) promises outstanding magneto-electric effects to happen in these compounds. Notably, GVS is the first and only multiferroic material known to date that potentially might find its way into top-modern applications such as skyrmionic memories. In order to significantly advance the fundamental understanding, we propose in this bilateral project to shed light onto the fundamental static and dynamic behavior of GVS and its related compounds, through the concerted nanoscale approach between theory and experiment. More precisely, we uniquely combine the local-scale experimental inspection (by using various scanning probe techniques and optical spectroscopy) with multi-scale modeling strategies (i.e. ab-initio, phase field modeling, etc.). The two participating teams in Prague/Czech Republic (theory) and Dresden/Germany (experiment) form the ideal basis in order to conduct this research in the proposed bilateral project.The project goals thus are threefold: Firstly, the mechanism of magneto-electric coupling in the GVS and other family members such as GeV4S8, GaMo4S8, GaV4Se8 need a comprehensive and fundamental understanding that can be obtained through our concerted and complementary theoretical and experimental efforts, only. Secondly, all these compounds will be subjected to external stimuli such as mechanical strain, electric, magnetic and optical fields in order to purposely impact the phase diagram of the skyrmionic phases in these unique materials; for instance, we expect the magnetic textures, i.e. the cycloidal / skyrmionic lattice to rotate into energetically favorable directions. Thirdly, these stimuli will allow also to study the dynamical properties of these materials on the local 1-nm length scale.