Magnetism in the two-dimensional t- t′ Hubbard model: From low- to over-doping

Abstract

Based on quantum Monte Carlo calculations, we shall discuss the regime where ferromagnetic correlation is dominant in the two-dimensional t- t′ Hubbard model at a finite temperature. In this model, ferromagnetism competes with antiferromagnetism and we reveal how crossover occurs between them at a finite temperature by the bias-free method. We shall investigate the data in the context of the so-called "low-density ferromagnetism." The weak-coupling result is also shown and the data are compared with the "Nagaoka ferromagnetism." © 2005 The American Physical Society.