METALLIC FERROMAGNETISM IN A SINGLE-BAND MODEL .4. EFFECT OF PAIR HOPPING

被引:43
作者
HIRSCH, JE
机构
[1] Department of Physics, University of California at San Diego, San Diego
来源
PHYSICAL REVIEW B | 1991年 / 43卷 / 01期
关键词
D O I
10.1103/PhysRevB.43.705
中图分类号
T [工业技术];
学科分类号
08 ;
摘要
The Coulomb-exchange matrix element between electrons in nearest-neighbor Wannier orbitals J has recently been proposed to play a fundamental role in metallic ferromagnetism. In addition to exchanging electrons on nearest-neighbor sites, it gives rise to a pair-hopping contribution to the Hamiltonian. Here we examine the effect of the pair-hopping term on the tendency to ferromagnetism. It is stressed that the important role that these interactions play in ferromagnetism results from their momentum dependence in the solid-state environment. We find that the tendency to ferromagnetism is further enhanced by the pair-hopping term, and the parameter range where unsaturated ferromagnetism occurs is enlarged. Its effect becomes small for large on-site repulsion U. The combination of exchange and pair hopping gives rise to bond-charge repulsion, and metallic ferromagnetism can be understood as arising from the tendency of electrons to avoid this direct Coulomb interaction.
引用
收藏
页码:705 / 711
页数:7
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