Surface energy and elementary excitations of the XYZ spin chain with integrable open boundary fields

TL;DR

This paper analyzes the surface energy and elementary excitations of the anisotropic XYZ spin chain with open boundary conditions, providing exact results and exploring boundary effects on physical properties.

Contribution

It introduces a new parametrization scheme to exactly determine surface and excitation energies despite broken symmetry.

Findings

Surface and excitation energies depend on the parity of the number of sites.

Distribution patterns of zero roots are characterized for ground and excited states.

Surface energy and excitations are obtained for various boundary parameters.

Abstract

We study the thermodynamic limit of the anisotropic XYZ spin chain with non-diagonal integrable open boundary conditions. Although the $U(1)$-symmetry is broken, by using the new parametrization scheme, we exactly obtain the surface energy and the excitation energy of the system, which has solved the difficulty in the inhomogeneous $T-Q$ relation. With the boundary parameters in the regions making the Hamiltonian Hermitian, we have obtained the distribution patterns of the zero roots of the eigenvalue of the transfer matrix for the ground state and the excited ones. We find that the surface and excitation energies depend on the parities of sites number $N$, due to the long-range Neel order in the bulk. The spontaneous magnetization and easy-axis for all the regions of boundary parameters are studied. We also obtain the physical quantities in the thermodynamic limit of boundary XXZ model by taking the triangular limit.