A microscopic model for D-wave pairing in the cuprates: what happens when electrons somersault?

Abstract

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.

Magnetic structure factor in cuprate superconductors: Evidence for charged meron vortices

“…In this quantum state, electrons undergo a 2 rotation (somersault) in their internal space of Euler angles as they traverse an elementary closed loop (plaquette) of the two-dimensional (2D) lattice. This lowers the many-body energy relative to that of a conventional AFM and has the immediate consequence that at half filling, the effective one-electron dispersion relations quantitatively agree with the ARPES data 20,21 without the need for ad hoc band structure parameters. 12 The incorporation of the correct one-electron dispersion from the outset then reveals that doping leads to the nucleation of merons and antimerons.…”

“…We have shown that the merons are mobile charged bosons, [19][20][21] since the magnetic vortex carries a total spin zero and traps exactly one hole. This bosonic nature of the charge carriers provides a natural and compelling mechanism for the non-Fermi metal observed above the superconducting phase.…”

“…1). They are nucleated upon doping a modified version of the Hubbard model, [19][20][21] in which the FIG. 1.…”

“…This microscopic model also provides a unified description (with no free or adjustable parameters) for the observed midinfrared optical absorption, destruction of long-range AFM order with doping and aspects of ARPES. [19][20][21] It was independently suggested 23,24 that this modified Hubbard model, called the spin-flux model, can be derived from a fundamental, previously unrecognized, kinematic property of spin-1 / 2 electrons as they execute a closed trajectory in coordinate space. This concept is entailed in the proposition that a type of many-electron wave function underlies the observed antiferromagnetic spin liquid.…”