Cyclic four-spin exchange on a two-dimensional square lattice: Possible applications in high-Tc superconductors

M. Roger; J. M. Delrieu

doi:10.1103/PhysRevB.39.2299

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Cyclic four-spin exchange on a two-dimensional square lattice: Possible applications in high-Tc superconductors

M. Roger, J. M. Delrieu

DOI 10.1103/PhysRevB.39.2299 · Physical Review B

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Abstract

In the planar CuO2 square lattice of new superconductors, the small energy difference of conducting holes between Cu and O sites, compared to the relatively large on-site energy for double occupancy, might favor cyclic four-hole exchange via intermediate O sites rather than superexchange processes, as in solid He3. The properties of the four-spin exchange and Heisenberg Hamiltonians are compared in two dimensions through exact diagonalization on small clusters up to 18 spins. Four-spin exchange could explain the large inelasticity observed in neutron and two-magnon Raman spectroscopy, and resolve some discrepancies between exchange frequencies deduced from Raman and susceptibility data.