School of Physical Science and Technology, ShanghaiTech University, Shanghai 200031, China.
National Laboratory of Solid-State Microstructures, College of Engineering and Applied Sciences, and Collaborative Innovation Center of Advanced Microstructures, Nanjing University, Nanjing 210093, People's Republic of China.
Phys Rev Lett. 2019 Jul 26;123(4):047203. doi: 10.1103/PhysRevLett.123.047203.
The recent discovery of intrinsic ferromagnetic order in the atomically thin van der Waals crystal CrXTe_{3} (X=Si, Ge) stimulates intensive studies on the nature of low-dimensional magnetism because the presence of long-range magnetic order in two-dimensional systems with continuous symmetry is strictly prohibited by thermal fluctuations. By combining advanced many-body calculations with angle-resolved photoemission spectroscopy we investigate CrSiTe_{3} single crystals and unveil the pivotal role played by the strong electronic correlations at both high- and low-temperature regimes. Above the Curie temperature (T_{c}), Coulomb repulsion (U) drives the system into a charge transfer insulating phase. In contrast, below T_{c} the crystal field arranges the Cr-3d orbitals such that the ferromagnetic superexchange profits, giving rise to the bulk ferromagnetic ground state with which the electronic correlations compete. The excellent agreement between theory and experiment establishes CrSiTe_{3} as a prototype low-dimensional crystal with the cooperation and interplay of electronic correlation and ferromagnetism.
最近在原子层范德瓦尔斯晶体 CrXTe3（X=Si，Ge）中发现了本征铁磁有序，这激发了对低维磁性质的深入研究，因为在具有连续对称性的二维系统中，长程磁有序受到热涨落的严格限制。通过结合先进的多体计算和角分辨光发射谱，我们研究了 CrSiTe3 单晶，并揭示了强电子相关在高温和低温区都起着关键作用。在居里温度（Tc）以上，库仑排斥（U）使系统进入电荷转移绝缘相。相比之下，在 Tc 以下，晶体场排列 Cr-3d 轨道，使铁磁超交换受益，从而产生与电子相关竞争的体铁磁基态。理论与实验之间的良好一致性确立了 CrSiTe3 作为一个具有电子相关和铁磁体合作和相互作用的原型低维晶体。
