ATTRACTIVE HUBBARD-MODEL ON A TRIANGULAR LATTICE

We study the attractive (i.e., negative-U) Hubbard model on a triangular lattice. A strong-coupling analysis indicates that a charge-density-wave (CDW) state cannot be formed for any band filling due to frustration, while pairing correlations are robust. Quantum Monte Carlo simulations confirm the absence of a CDW state for intermediate couplings, and show that the critical temperature for superconductivity is higher close to half-filling, unlike the square lattice. Also, the behavior of the uniform magnetic susceptibility suggests that the precursor spin-gap phase is not affected by frustration.