Evolution of the low-energy excitation spectrum from the pure Hubbard ladder to the SO(5) ladder: A numerical study

Abstract

The Hubbard Hamiltonian on a two-leg ladder is studied numerically using quantum Monte Carlo and exact diagonalization techniques. A rung interaction, V, is turned on such that the resulting model has an exact SO(5) symmetry when V={minus}U. The evolution of the low-energy excitation spectrum is presented from the pure Hubbard ladder to the SO(5) ladder. It is shown that the low-energy excitations in the pure Hubbard ladder have an approximate SO(5) symmetry. {copyright} {ital 1998} {ital The American Physical Society}