Ground State of a One-Dimensional Antiferromagnetic Anisotropic Heisenberg Model with Free Boundary Conditions

摘要

Conditions of appearance and momenta of the mixed states parametrized by real and imaginary momenta are determined by analyzing the exact solution to the one-dimensional open XXZ-model in the class of antiferromagnetic states with m=N/2 inverted spins. It has been shown that a harmonic antiferromagnetic state, which is an N/2 magnon superposition with real momenta, is unstable with respect to the appearance of "easy axis" exchange anisotropy. In this case, the ground state of the antiferromagnetic open XXZ-model is a mixed state with an imaginary momentum determined by anisotropy.