Institut de Physique et Chimie des Matériaux de Strasbourg, UMR7504, CNRS-UdS, Strasbourg, France.
Phys Rev Lett. 2011 Jun 3;106(22):226401. doi: 10.1103/PhysRevLett.106.226401. Epub 2011 May 31.
We investigate the edge-state magnetism of graphene nanoribbons using projective quantum Monte Carlo simulations and a self-consistent mean-field approximation of the Hubbard model. The static magnetic correlations are found to be short ranged. Nevertheless, the correlation length increases with the width of the ribbon such that already for ribbons of moderate widths we observe a strong trend towards mean-field-type ferromagnetic correlations at a zigzag edge. These correlations are accompanied by a dominant low-energy peak in the local spectral function and we propose that this can be used to detect edge-state magnetism by scanning tunneling microscopy. The dynamic spin structure factor at the edge of a ribbon exhibits an approximately linearly dispersing collective magnonlike mode at low energies that decays into Stoner modes beyond the energy scale where it merges into the particle-hole continuum.
我们使用投影量子蒙特卡罗模拟和 Hubbard 模型的自洽平均场近似来研究石墨烯纳米带的边缘态磁性。发现静态磁关联具有短程性质。然而，关联长度随着带的宽度增加而增加，以至于对于中等宽度的带，我们在锯齿形边缘观察到强烈的朝着平均场型铁磁关联的趋势。这些关联伴随着局域谱函数中的主导低能峰值，我们提出可以通过扫描隧道显微镜来检测边缘态磁性。带边缘的动态自旋结构因子在低能下表现出近似线性色散的集体磁振子模式，该模式在能量尺度上衰减为 Stoner 模式，超过该能量尺度后，它与粒子-空穴连续体合并。
