Variational model for one-dimensional quantum magnets

TL;DR

This paper introduces a novel variational method using a non-local trial wave function to analyze ground states and correlations in 1D quantum magnets, demonstrated on the XXZ chain with potential for broader applications.

Contribution

It presents a new variational approach with an analytic energy expression for 1D quantum magnets, improving analysis of ground states and correlations.

Findings

Analytic energy calculation as a function of variational parameters

Application to XXZ spin-1/2 chain under magnetic field

Discussion of method's generalizations and applications

Abstract

A new variational technique for investigation of the ground state and correlation functions in 1D quantum magnets is proposed. A spin Hamiltonian is reduced to a fermionic representation by the Jordan-Wigner transformation. The ground state is described by a new non-local trial wave function, and the total energy is calculated in an analytic form as a function of two variational parameters. This approach is demonstrated with an example of the XXZ-chain of spin-1/2 under a staggered magnetic field. Generalizations and applications of the variational technique for low-dimensional magnetic systems are discussed.