Unusually flat hole dispersion relation in the two-dimensional Hubbard model and restoration of coherence by addition of pair-hopping processes

Abstract:

The dispersion relation of a doped hole in the half-filled 2D Hubbard model is shown to follow a |k|⁴ law around the $(0, \pm \pi )$ and $( \pm \pi ,0)$points in the Brillouin zone. Upon addition of pair-hopping processes this dispersion relation is unstable towards a |k|⁴ law. The above follows from T=0 Quantum Monte-Carlo calculations of the single particle spectral function A(κ,ω) on 16 X 16 lattices. We discuss finite dopings and argue that the added term restores coherence to charge dynamics and drives the system towards a d _{x2 - y2} superconductor.