Fluctuation effects of nonlinear coupling between spin and charge excitations on dynamical correlation functions of the one-dimensional extended Hubbard model

We study fluctuation effects of nonlinear coupling between spin and charge excitations on dynamical correlation functions of the one-dimensional extended Hubbard model at half-filling. Two kinds of dynamical correlation functions, dynamical spin- and charge-correlation functions, are calculated by means of a quantum Monte Carlo simulation We show that the dynamical spin-correlation function has a new peak on the high-energy side of the well-known magnon peak. Since this peak always appears above the charge-excitation gap, it should originate from a charge fluctuation induced through a final-state interaction of magnon creation. rme also show that in the dynamical charge-correlation function, a charge-transfer excitation peak is broadened by fluctuation effects due to magnons. These results clearly show that spin and charge excitations are nonlinearly coupled in this system.