Exact solutions and elementary excitations in the XXZ spin chain with unparallel boundary fields

TL;DR

This paper derives exact solutions for the XXZ spin chain with unparallel boundary fields, revealing unique elementary excitations and ground states, and analyzing their correlation functions and spin properties.

Contribution

It introduces a method to solve the XXZ spin chain with unparallel boundary fields using algebraic Bethe ansatz, uncovering novel excitations and ground states.

Findings

Elementary excitations are spinons without definite spin in the easy-plane case.

A spiral ground state is realized in the easy-axis ferromagnetic case.

Correlation functions and spin properties are explicitly derived.

Abstract

By using a set of gauge transformations, the exact solutions of the XXZ spin chain with unparallel boundary magnetic fields are derived in the framework of the algebraic Bethe ansatz. In the easy-plane case, we show the elementary excitations are some kind of spinons without definite spin because the U(1) symmetry is broken, while in the easy-axis ferromagnetic case a spiral state is realized in the ground state. The correlation functions, the spin torque as well as the spin voltage for the later case are also derived.