Electronic Hamiltonian and antiferromagnetic interactions in La2CuO4.

Abstract

A many-body Hamiltonian for ${\mathrm{La}}_{2}$${\mathrm{CuO}}_{4}$ with ab initio parameters is solved numerically using embedded-cluster approximations. The results give an antiferromagnetic insulator with a 2--3 eV energy gap, consistent with spectroscopic measurements, NMR chemical shifts, and the spin-wave velocity. The N\'eel state has a significant frustration due to second-neighbor interactions, ${J}_{2}$/${J}_{1}$\ensuremath{\approxeq}5%--8%. Two competing states are found for holes introduced by doping, with primarily in-plane oxygen ${p}_{\ensuremath{\sigma}}$ and out-of-plane oxygen ${p}_{z}$ character.