We investigate the interaction-induced deformation of the Fermi surface in the two-dimensional Hubbard model on the triangular lattice in the weak-coupling regime within the second-order perturbation theory. In systems without frustration, at the filling equal to or close to half-filling, the direction of the deformation of the Fermi surface is the direction toward the Fermi surface at half-filling with the smaller transfer amplitude set to zero, whose nesting vector is commensurate with the underlying lattice. On the other hand, in systems with frustration, the Fermi surface is not deformed by the interaction because of the frustration.

• Received 5 October 1998

DOI:https://doi.org/10.1103/PhysRevB.60.7886