Quantum integrable matrix models of spinor Bose gases in one spatial dimension

TL;DR

This paper develops a quantum integrable matrix model for spinor Bose gases in one dimension, deriving Bethe equations, thermodynamic properties, and analyzing bound states and exclusion principles.

Contribution

It introduces a matrix extension of the nonlinear Schrödinger model for spinor Bose gases, generalizing previous techniques to arbitrary spin multiplets and interactions.

Findings

Eigenstates constructed via algebraic Bethe-ansatz for arbitrary matrix sizes.

Derived Bethe equations for spectra of conserved quantities.

Computed ground state phase diagram and analyzed bound states.

Abstract

Degenerate spinor Bose gases with repulsive density-density interaction and anti-ferromagnetic spin-spin coupling in one spatial dimension are shown to be described by a quantum integrable matrix extension of the nonlinear Schr\"odinger model, whose fundamental fields are described by an $m\,\times\,n$ matrix of bosonic field operators. The eigenstates of this model are constructed for arbitrarily sized matrix field operators by means of algebraic Bethe-ansatz techniques, and the corresponding Bethe equations governing the spectra of conserved quantities are derived. The approach thus generalizes previously chosen techniques to account for arbitrary spin multiplets and their spin-spin interaction. Focusing on the specific case of the $2\times2$ model, which is shown to correspond to a spin-$1$ Bose gas, a set of integral equations is derived, which describe its equilibrium thermodynamic properties. From these, the ground state phase diagram is computed both, numerically and analytically in the parameter plane spanned by the chemical potential and an external magnetic field. Furthermore, the existence of paired bound states is shown to modify the Pauli exclusion principle for interacting bosons in one dimension. In particular, it is found that no two quasiparticle rapidities can coincide, provided that the Lieb parameter satisfies $\gamma>4/3$.