Anomalous Correlation Functions in Low-Dimensional Oxides: An Effect of Orbital Degrees of Freedom?

Abstract

It is now well admitted that the orbital degrees of freedom play an important role in the occurrence of non-conventional properties in many low-dimensional highly-correlated electron systems. Thus, in quasi-2D high-Tc cuprates the existence of staggered orbital currents has been invoked to explain the peculiarities of the pseudo-gap phase. In these materials, the quantitative understanding requires to take into account the multi-spin exchange interactions, as well. Among other effects, electron circulations or exchanges should give rise to anomalous magnetic correlation functions, which can be accurately investigated by means of polarized neutron scattering. This will be illustrated by recent studies carried out on the spin-ladder Sr14Cu24O41 and on the quasi-2D helimagnet BaCo2As2O8. * )