Yao Fengrui, Rossi Dario, Gabrovski Ivo A, Multian Volodymyr, Hua Nelson, Watanabe Kenji, Taniguchi Takashi, Gibertini Marco, Gutiérrez-Lezama Ignacio, Rademaker Louk, Morpurgo Alberto F
Department of Quantum Matter Physics, University of Geneva, Geneva, Switzerland.
Group of Applied Physics, University of Geneva, Geneva, Switzerland.
Nat Commun. 2024 Nov 29;15(1):10377. doi: 10.1038/s41467-024-54870-2.
Interfaces between twisted 2D materials host a wealth of physical phenomena originating from the long-scale periodicity associated with the resulting moiré structure. Besides twisting, an alternative route to create structures with comparably long-or even longer-periodicities is inducing a differential strain between adjacent layers in a van der Waals (vdW) material. Despite recent theoretical efforts analyzing its benefits, this route has not yet been implemented experimentally. Here we report evidence for the simultaneous presence of ferromagnetic and antiferromagnetic regions in CrBr-a hallmark of moiré magnetism-from the observation of an unexpected magnetoconductance in CrBr tunnel barriers with ferromagnetic FeGeTe and graphene electrodes. The observed magnetoconductance evolves with temperature and magnetic field as the magnetoconductance measured in small-angle CrBr twisted junctions, in which moiré magnetism occurs. Consistent with Raman measurements and theoretical modeling, we attribute the phenomenon to the presence of a differential strain in the CrBr multilayer, which locally modifies the stacking and the interlayer exchange between adjacent CrBr layers, resulting in spatially modulated spin textures. Our conclusions indicate that inducing differential strain in vdW multilayers is a viable strategy to create moiré-like superlattices, which in the future may offer in-situ continuous tunability even at low temperatures.
扭曲的二维材料之间的界面呈现出大量源自与所得莫尔条纹结构相关的长尺度周期性的物理现象。除了扭曲之外，在范德华（vdW）材料中相邻层之间引入差分应变是创建具有相当长甚至更长周期性结构的另一种途径。尽管最近有理论研究分析了其益处，但这种途径尚未通过实验实现。在这里，我们通过观察具有铁磁FeGeTe和石墨烯电极的CrBr隧道势垒中意外的磁电导，报告了CrBr中同时存在铁磁和反铁磁区域的证据——这是莫尔条纹磁性的一个标志。观察到的磁电导随温度和磁场而变化，就像在发生莫尔条纹磁性的小角度CrBr扭曲结中测量的磁电导一样。与拉曼测量和理论建模一致，我们将该现象归因于CrBr多层膜中存在差分应变，该应变局部改变了相邻CrBr层之间的堆叠和层间交换，从而导致空间调制的自旋纹理。我们的结论表明，在vdW多层膜中引入差分应变是创建类莫尔超晶格的一种可行策略，未来即使在低温下也可能提供原位连续可调性。
