Contribution of the non-Heisenberg ring exchange to the magnetic mechanism of high-T c superconductivity

Abstract

The effect of non Heisenberg four spin ring exchange on the superconducting transition temperature in strongly correlated electron systems is studied. It is shown that the ring exchange can significantly suppress the contribution of the Heisenberg exchange to superconducting pairing.

Magnetic Interactions in Molecules and Highly Correlated Materials: Physical Content, Analytical Derivation, and Rigorous Extraction of Magnetic Hamiltonians

“…Some well-known examples of the necessity of introducing additional interactions in the model Heisenberg Hamiltonian belong to the solid-state physics field. To fully understand the magnetic excitations and the infrared and neutron scattering spectra of 2D − and spin ladder cuprates, , parent compounds of the high- T c superconductor cuprates, the spin Hamiltonian has to be extended with second-neighbor magnetic coupling J NNN and four-spin cyclic exchange terms J ring . The J ring terms originate in the cyclic movement of the electrons around the Cu 4 O 4 plaquettes.…”

“…The J ring terms originate in the cyclic movement of the electrons around the Cu 4 O 4 plaquettes. It has been proposed that the resulting current plays an important role in the mechanism of superconductivity. , Similar four-body terms are crucial to describe the ground-state properties of 3 He, and they are also present in π conjugated systems …”

Effective indirect multi-site spin–spin interactions in the s–d(f) model

“…From equation (17) it follows, that at f 1 = f 2 the second order effective action Ξ 2 describes indirect exchange interaction of two localized spins through the subsystem of itinerant electrons. However, in contrast to the usual RKKY-interaction here the retardation effects, caused by τ -dependence of V 2 , are taken into account.…”

“…In the paper [16] it was argued that ring exchange is important to describe magnetic properties of cuprate high-temperature superconductors. Effect of ring exchange interaction on the superconductivity in cuprates was investigated in [17].…”