C. Honerkamp et al., Breakdown of the Landau-Fermi liquid in two dimensions due to umklapp scattering - art. no. 035109, PHYS REV B, 6303(3), 2001, pp. 5109
We study the renormalization-group (RG) flow of interactions in the two-dim
ensional t-t' Hubbard model near half-filling in an N-patch representation
of the whole Fermi surface. Starting from weak to intermediate couplings th
e flows are to strong coupling, with different characters depending on the
choice of parameters. In a large parameter region elastic umklapp scatterin
gs drive an instability which on parts of the Fermi surface exhibits the ke
y signatures of an insulating spin liquid (ISL), as proposed by Furukawa, R
ice, and Salmhofer [Phys. Rev. Lett. 81, 3195 (1998)] rather than a convent
ional symmetry-broken state. The ISL is characterized by both strong d-wave
pairing and antiferromagnetic correlations; however, it is insulating due
to the vanishing local charge compressibility and a spin liquid because of
the spin gap arising from the pairing correlations. We find that the unusua
l RG flow, which we interpret in terms of an ISL, is a consequence of a Fer
mi surface close to the saddle points at the Brillouin-zone boundaries whic
h provides an intrinsic and mutually reinforcing coupling between pairing a
nd umklapp channels.