A Microscopic Model for D-Wave Pairing in the Cuprates: What Happens   when Electrons Somersault?
  We present a microscopic model for a strongly repulsive electron gas on a 2D square lattice. We suggest that nearest neighbor Coulomb repulsion stabilizes a state in which electrons undergo a "somersault" in their internal spin-space (spin-flux). When this spin-1/2 antiferromagnetic (AFM) insulator is doped, the charge carriers nucleate mobile, charged, bosonic vortex solitons accompanied by unoccupied states deep inside the Mott-Hubbard charge-transfer gap. This model provides a unified microscopic basis for (i) non-Fermi-liquid transport properties, (ii) mid-infrared optical absorption, (iii) destruction of AFM long range order with doping, (iv) angled resolved spectroscopy (ARPES), and (v) d-wave preformed charged carrier pairs. We use the Configuration Interaction (CI) method to study the quantum translational and rotational properties of such pairs. The CI method systematically describes fluctuation and quantum tunneling corrections to the Hartree-Fock approximation and recaptures essential features of the (Bethe ansatz) exact solution of the Hubbard model in 1D. For a single hole in the 2D AFM plane, we find a precursor to spin-charge separation. The CI ground state consists of a bound vortex-antivortex pair, one vortex carrying the charge and the other one carrying the spin of the doping hole. 
Mona Berciu and Sajeev John