Stability of ferromagnetism in the Hubbard model on the kagome lattice.
Stability of ferromagnetism in the Hubbard model on the kagome lattice.
复制标题
Kagome 晶格的 Hubbard 模型中铁磁性的稳定性。
作者：
A. Tanaka;H. Ueda
Kagome晶格上的Hubbard模型在相应的单电子问题中具有高度简并的基态(平坦的最低能带)，在多电子基态中表现出所谓的平带铁磁性，正如Mielke[J.Phys]所发现的那样。A 24、L73(1991)]]。在这里，我们研究通过在上述模型中添加额外的跳跃项而得到的模型。最低的单电子带变得色散，最低的带与另一个带之间没有带隙。我们证明了，当最低能带接近平坦时，当最低能带半充满时，该微扰模型的基态仍保持饱和铁磁性。
The Hubbard model on the kagome lattice has highly degenerate ground states (the flat lowest band) in the corresponding single-electron problem and exhibits the so-called flat-band ferromagnetism in the many-electron ground states as was found by Mielke [J. Phys. A 24, L73 (1991)]]. Here we study the model obtained by adding extra hopping terms to the above model. The lowest single-electron band becomes dispersive, and there is no band gap between the lowest band and the other band. We prove that, at half filling of the lowest band, the ground states of this perturbed model remain saturated ferromagnetic if the lowest band is nearly flat.