Indications of unconventional superconductivity in doped and undoped triangular antiferromagnets

The possibility of superconductivity in doped and undoped triangular antife rromagnets is discussed. Using the Bethe-SaIpeter (BS) equation, it is show n that the exchange of random-phase approximation paramagnons on a triangul ar lattice Hubbard model leads to strong pairing correlations at and near h alf filling. The dominant states for this system correspond to d-wave singl et (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 compou nds kappa-(BEDT-TTF)(2)X are discussed. [S0163-1829(99)50202-6].