Ring Exchange and Correlated Fermions
arXiv:cond-mat/0504141 · doi:10.1016/j.jpcs.2005.05.065
Abstract
The concept of exchange in strongly-correlated fermions is reviewed with emphasis on the generalization of the Heisenberg pair exchange to higher order n-particle permutations. The "frustration" resulting from competing ferromagnetic three-spin exchange and antiferromagnetic two- and four-spin exchanges is illustrated on a two-dimensional model system: solid 3He films. Recent experimental results proving the presence of four-spin exchange interactions in the CuO2 plaquettes of high Tc cuprates are reported.
Invited talk at ISSP9 Conference Tokyo, Japan, November 2004 10 pages