Indications of unconventional superconductivity in doped and undoped triangular antiferromagnets

The possibility of superconductivity in doped and undoped triangular antiferromagnets is discussed. Using the Bethe-SaIpeter (BS) equation, it is shown that the exchange of random-phase approximation paramagnons on a triangular lattice Hubbard model leads to strong pairing correlations at and near half filling. The dominant states for this system correspond to d-wave singlet (even-frequency) and a-wave triplet (odd-frequency) pairing. Analytical techniques applied to the hole-doped t-J model yield similar results. A t(1)-t(2) Hubbard model interpolating between square (t(1)=0) and triangular (t(1)=t(2)) lattices has a tendency to only d-wave singlet pairing for t(1)/t(2)less than or equal to 0.8. Experimental consequences for organic compounds kappa-(BEDT-TTF)(2)X are discussed. [S0163-1829(99)50202-6].