Direct analytic continuation of the self-energy is used to determine the effect of antiferromagnetic ordering on the spectral function and optical conductivity of a Mott insulator. Comparison of several methods shows that the most robust estimation of the gap value is obtained by use of the real part of the continued self-energy in the quasiparticle equation within the single-site dynamical mean-field theory of the two-dimensional square lattice Hubbard model, where, for a $U$ that is slightly greater than the Mott critical value, antiferromagnetism increases the gap by about 80%.

• Received 13 April 2009

DOI:https://doi.org/10.1103/PhysRevB.80.045101