Integrable spin-boson models descending from rational six-vertex models

TL;DR

This paper constructs integrable spin-boson models using quantum inverse scattering, revealing new Hamiltonians with both rotating and counter-rotating terms, and discusses their spectral properties and solvability.

Contribution

It introduces a method to derive integrable spin-boson models from rational vertex models with specific boundary conditions, including non-hermitian and hermitian cases.

Findings

Open boundary conditions yield integrable Hamiltonians with mixed interaction terms.

Spectrum can be obtained via algebraic Bethe ansatz under certain conditions.

Hermitian Hamiltonians are obtained in a quasi-classical limit, but their diagonalization remains open.

Abstract

We construct commuting transfer matrices for models describing the interaction between a single quantum spin and a single bosonic mode using the quantum inverse scattering framework. The transfer matrices are obtained from certain inhomogeneous rational vertex models combining bosonic and spin representations of SU(2), subject to non-diagonal toroidal and open boundary conditions. Only open boundary conditions are found to lead to integrable Hamiltonians combining both rotating and counter-rotating terms in the interaction. If the boundary matrices can be brought to triangular form simultaneously, the spectrum of the model can be obtained by means of the algebraic Bethe ansatz after a suitable gauge transformation; the corresponding Hamiltonians are found to be non-hermitian. Alternatively, a certain quasi-classical limit of the transfer matrix is considered where hermitian Hamiltonians are obtained as members of a family of commuting operators; their diagonalization, however, remains an unsolved problem.