Dimer states in the one-dimensionalt-J-J’ model

Abstract

We introduced variational wave functions to describe dimer states in the one-dimensional t-J-J’ model, when one hole is doped and J’=J/2. For finite J/‖t‖ in the first excited state with S=1, there exists a bound state of the hole and an unpaired electron. For the choice of J/‖t‖=2, the spin gap is ${\mathrm{\Delta }}^{\mathrm{var}}$=0.181J and is smaller than the value of the corresponding spin system, ${\mathrm{\Delta }}_0^{\mathrm{var}}$=0.25J. The existence of the bound state suggests that the excited state as a function of the electron density is discontinuous at half-filling if J/‖t‖ is finite.