Ferromagnetism in the Hubbard model
Ferromagnetism in the Hubbard model
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DOI：
10.1088/0953-8984/3/26/014
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发表时间：
1991-07
期刊：
影响因子：
--
通讯作者：
W von der Linden;D M Edwards
中科院分区：
文献类型：
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作者：
W von der Linden;D M Edwards
在最近邻跳跃的正方晶格Hubbard模型中，研究了自旋完全对准铁磁态对自旋反转的稳定性。一个变分的ananimals，这是准确的，在一维和准确的结果相比，小集群产生几乎准确的结果，在二维的情况下。绘制了（W/U，delta）相图中的铁磁区，其中W为带宽，U为电子相互作用，delta为每个原子的空穴数。这个区域比以前的变分计算小得多，并且严格地得出结论，对于所有的U，当δ>0.29时，完全自旋对准的状态是不稳定的，对于所有的δ，当W/U>0.19时，完全自旋对准的状态是不稳定的。的性质的不稳定性，并在铁磁状态的低洼激发不同的三角洲和W/V，进行了讨论。
The stability of the ferromagnetic state with complete spin alignment against a single spin reversal is studied in the square-lattice Hubbard model with nearest-neighbour hopping. A variational ansatz is used, which is exact in one dimension and by comparison with accurate results for small clusters yields almost exact results in the two-dimensional case. The ferromagnetic region in the (W/U, delta ) phase diagram is mapped out, where W is the bandwidth, U the on-site electron interaction and delta is the number of holes per atom. This region is considerably smaller than in previous variational calculations and it is rigorously concluded that the state of complete spin alignment is unstable when delta >0.29, for all U, and when W/U>0.19, for all delta . The nature of the instability, and of the low-lying excitations in the ferromagnetic state for varying delta and W/V, is discussed.