Adjacent spin operator dynamical structure factor of theS = 1/2 Heisenberg chain

Abstract

Considering the adjacent spin operatorsSjzSj + 1z andSj − Sj + 1 − inthe S = 1/2 Heisenberg chain, we give a determinant representation of their form factors.The dynamical structure factors of the respective operators are computed overthe whole Brillouin zone in several magnetic fields and the resulting signal isanalyzed in terms of excitation types. Among other results, we find that theSjzSj + 1z dynamical structure factor carries a large weight of the four-spinon excitations which aredistinguishable from the two-spinon signal because they are located outside the two-spinonspectrum.