On Dimer Pairing Mechanism of Superconductivity

Physical properties in a dimer pairing superconductor are examined. The pairing has a finite net momentum and breaks lattice translational symmetry as well as the gauge symmetry. The mean field equations for the dimerized t-J model and the spin-Peierls t-J model are solved numerically to discuss novel features of the dimer pairing mechanism. The dynamical spin susceptibility is calculated to discuss spin excitations in the superconducting state. The energy gap opens over the Fermi surface without nodes, while the Hebel-Slichter peak is absent in the NMR relaxation rate.