论文标题
MoiréFlatband Ferromagnetism的量子几何形状和稳定性
Quantum Geometry and Stability of Moiré Flatband Ferromagnetism
论文作者
论文摘要
各种扭曲的双层创建的几种Moiré系统在平板条件下表现出磁性，从而增强了相互作用的效果。从理论上讲，我们研究了Moiré平板铁磁对集体激发的稳定性，重点是Bloch带量子几何形状的影响。使用不同的方法（包括伯特盐底方方程，单模式近似值和分析理论）计算自旋镁光谱。我们的主要结果之一是根据库仑相互作用电位，浆果曲率和量子度量张量的旋转刚度的分析表达，其中最后两个数量表征了moiré频段的量子几何形状。该分析理论表明，浆果曲率在僵硬的旋转镁中起着重要作用。此外，我们为磁化波动构建了一个有效的场理论，并明确表明了Skyrmion激励结合了与Bloch带数量成正比的整数电子和Skyrmion绕组数。
Several moiré systems created by various twisted bilayers have manifested magnetism under flatband conditions leading to enhanced interaction effects. We theoretically study stability of moiré flatband ferromagnetism against collective excitations, with a focus on the effects of Bloch band quantum geometry. The spin magnon spectrum is calculated using different approaches, including Bethe-Salpeter equation, single mode approximation, and an analytical theory. One of our main results is an analytical expression for the spin stiffness in terms of the Coulomb interaction potential, the Berry curvatures, and the quantum metric tensor, where the last two quantities characterize the quantum geometry of moiré bands. This analytical theory shows that Berry curvatures play an important role in stiffening the spin magnons. Furthermore, we construct an effective field theory for the magnetization fluctuations, and show explicitly that skyrmion excitations bind an integer number of electrons that is proportional to the Bloch band Chern number and the skyrmion winding number.
