EXISTENCE OF HOLE POCKETS IN THE 2-DIMENSIONAL HUBBARD-MODEL

The electronic momentum distribution n(k) of the two-dimensional (2D) Hubbard model is studied for different values of the coupling U/t, electronic density n, and temperature, using quantum Monte Carlo techniques. A detailed analysis of the data on 8×8 clusters shows that along the line from (0,π) to (π,0) a minimum in n(k) at momenta k=(π/2,π/2) appears as the system is doped away from half-filling. In the range of couplings studied, the depth of this minimum is the largest at density n0.9, and it increases with decreasing temperature. Its existence is correlated with the strength of the antiferromagnetic correlations in the system. The apparent absence of structure at k=(π/2,π/2) in previous numerical studies of this model is explained. The results discussed here, together with the recent experimental data for the cuprates discussed by Aebi et al. [Phys. Rev. Lett. 72, 2757 (1994)], reopens the possibility that hole pockets exist in the doped 2D Hubbard model, although more evidence is needed to fully demonstrate their existence. © 1995 The American Physical Society.