Spin-Peierls State vs Néel State II. Interchain Exchange Interaction

Abstract

The ground state of the quasi-one-dimensional Heisenberg antiferromagnet coupled with the lattice distortion is determined on the basis of the phase Hamiltonian. By treating the weak interchain exchange interaction in a mean field approximation, it is shown within the self-consistent harmonic approximation that the ground state is either the Néel state or the spin-Peierls state as in the case of the small Ising anisotropy in our former investigation, but the Néel state is much more stabilized. The case of the staggered magnetic field is also examined. The three mechanisms, the Ising anisotropy, the interchain interaction, and the staggered field, are shown to be quite different in their stabilizing the Néel state. Comparison of these results with those by the classical treatment reveals the essential importance of the quantum fluctuations in the present competition problem.