Eur. Phys. J. B 37, 439-446 (2004)
https://doi.org/10.1140/epjb/e2004-00079-y

On the nature of the magnetic transition in a Mott insulator^*

¹ Max-Planck-Institut für Festkörperforschung, Heisenbergstrasse 1, 70569 Stuttgart, Germany
² University of Nijmegen, Toernooiveld 1, 6525 ED Nijmegen, The Netherlands
³ Institut für Theoretische Physik und Astrophysik, Universität Würzburg, Am Hubland, 97074 Würzburg, Germany
⁴ Marian Smoluchowski Institute of Physics, Jagellonian University, Reymonta 4, 30059 Kraków, Poland

Corresponding author: ^a a.m.oles@fkf.mpg.de

Received: 21 August 2003
Revised: 20 November 2004
Published online: 9 April 2004

Abstract

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.