Extended bound states of fermions on 2D square lattice beyond the nn hopping and interactions

TL;DR

This paper investigates how next-nearest-neighbour hopping and interactions influence extended bound states and pairing symmetries in a 2D square lattice Hubbard model, revealing the dominance of d-wave pairing and the existence of deep bound states.

Contribution

It provides an exact two-body solution showing nnn hopping favors d-wave pairing and characterizes the properties of bound states across the Brillouin zone.

Findings

d-wave pairing is strongly favored by nnn hopping

deep bound states can exist throughout the Brillouin zone

discovery of s*-d mixing in bound states

Abstract

We examine extended bound states in the dilute limit of the extended Hubbard model with next-nearest-neighbour (nnn) hopping and nnn interactions on the two dimensional square lattice. By the exact solution of a two-body problem we show that d-wave pairing is strongly favored by the nnn hopping. We determine the binding energies, mobilities and dispersion curves across Brillouin zone (B.z.) for bound states of various symmetries. The numerical analysis shows that the deep bound states can exist in the whole B.z. and we have also found s*-d mixing of the bound states.