On the nature of the magnetic transition in a Mott insulator

Using a combination of exact enumeration and the dynamical mean-field theory (DMFT) we study the drastic change of the spectral properties, obtained in the half-filled two-dimensional Hubbard model at a transition from an antiferromagnetic to a paramagnetic Mott insulator, and compare it with the results obtained using the quantum Monte Carlo method. The coherent hole (electron) quasiparticle spin-polaron subbands are gradually smeared out when the AF order disappears, either for increasing Coulomb repulsion U at fixed temperature T, or for increasing T at fixed U. Within the DMFT we present numerical evidence (a continuous disappearence of the order parameter) suggesting that the above magnetic transition is second order both in two and in three dimensions.Received: 20 November 2004, Published online: 9 April 2004PACS: 71.30. + h Metal-insulator transitions and other electronic transitions - 71.10.Fd Lattice fermion models (Hubbard model, etc.) - 79.60.-i Photoemission and photoelectron spectraThis work is dedicated to Professor Ole Krogh Andersen on the occasion of his 60th birthday.