Pairing-Symmetry Selection in a Weakly Doped Canted Antiferromagnet on the Triangular Lattice

Abstract

The mechanism of superconductivity generation by spin fluctuations in the electron doped canted antiferromagnet on the triangular lattice was analyzed. The underlying assumption is that the formation of the bound state is the prerequisite of pairing. The outcome of this analysis is also valid if an additional isotropic attraction is active but the anisotropic spin-fluctuation mediated force decides on the symmetry of the two-particle bound state. When the canted antiferromagnetic state is generated, the symmetry of the point group C6v for the triangular lattice is lowered to the symmetry of C3v. It is demonstrated that spin fluctuations definitely favor the p-wave bound state, which transforms according to the E representation of C3v. Since the inversion is not an element of C3v, the parity is not a good quantum number and thus the predicted paired state will be a mixture of singlet and triplet. Such a scenario may be relevant to physics of superconducting triangular cobaltates or organics.