Spin-orbital entanglement emerging from frustration in the Kugel-Khomskii model

Abstract

We investigate the zero-temperature phase diagrams of the bilayer square-lattice Kugel-Khomskii (d9) model involving entangled and singlet phases using mean-field cluster approach. This diagram includes interlayer singlet phase observed in copper fluoride K3Cu2F7 and exotic entangled spin-orbital phases. For a monolayer case, realized in K2CuF4, we perform similar calculations at finite temperature and show that the alternating-orbital ferromagnet decays first to an entangled uniform ferromagnet and then to a paramagnet. © Published under licence by IOP Publishing Ltd.