ELECTRONIC AND MAGNETIC-STRUCTURES OF CUPRATES WITH SPIN-ORBIT INTERACTION

The effective Hamiltonian for the CuO2 plane of high-T(c) cuprates is derived by taking into account the spin-orbit interaction. A finite-size exact-diagonalization technique is applied to the Hamiltonian, and the magnetic and electronic structures of the CuO2 plane in the low-temperature orthorhombic (LTO) and low-temperature tetragonal (LTT) phases of the La2CuO4-type crystals are examined. It is shown that the contribution from the in-plane oxygen 2p(z) orbital perpendicular to the plane is essential for the emergence of the weak ferromagnetism in the LTO-phase La2CuO4. In the LTT phase, either the uniaxial antiferromagnetism or the weak ferromagnetism is induced, depending on how the 2p(z) orbital contributes to the anisotropic superexchange interaction of the single Cu-O-Cu bond. We study the dynamics of a hole in an extended t-J model, and show that the lattice distortion works to change the symmetry of the electronic ground state via the spin-orbit coupling. The effect is, however, small and seems irrelevant to the anomalous properties of La1.88Ba0.12CuO4.