JETP Letters: issues online

Circulating current (CC) loops within the cuprate unit cell are proposed to play a key role in the physics of the pseudogap phase. However, main experimental observations motivated by this sophisticated proposal and seemingly supporting the CC model can be explained in frames of a simple and physically clear microscopic model. We argue that instead of a well-isolated Zhang-Rice (ZR) singlet ¹A_1g the ground state of the hole center [CuO₄]^5- (cluster analog of Cu³⁺ ion) in cuprates should be described by a complex ¹A_1g-^1,3B_2g-^1,3E_u multiplet, formed by a competition of conventional hybrid Cu 3d-O 2p $b_{1g}(\sigma)\propto d_{x^2 -y^2}$ state and purely oxygen nonbonding O 2pπ states with a_2g(π) and e_ux,y(π) symmetry. In contrast with inactive ZR singlet we arrive at several novel competing orbital and spin-orbital order parameters, e.g., Ising-like net orbital magnetic moment, orbital toroidal moment, intra-plaquette's staggered order of Ising-like oxygen orbital magnetic moments. As a most impressive validation of the non-ZR model we explain fascinating results of recent neutron scattering measurements that revealed novel type of magnetic ordering in pseudogap phase of several hole-doped cuprates.