Dynamics of an SO(5) symmetric ladder model

TL;DR

This paper explores an exactly SO(5) symmetric ladder model, demonstrating how it unifies antiferromagnetism and superconductivity through a bond-Boson framework, with implications for understanding correlated electron systems.

Contribution

It introduces an SO(5)-symmetric bond-Boson model for spin ladders, providing a simple example of SO(5) symmetry and analyzing its physical implications.

Findings

Exact eigenstates with SO(5) multiplets identified

Spectral fingerprints of SO(5) symmetry observed

Generalized rigid band behavior in photoemission spectra

Abstract

We discuss properties of an exactly SO(5) symmetric ladder model. In the strong coupling limit we demonstrate how the SO(3)-symmetric description of spin ladders in terms of bond Bosons can be upgraded to an SO(5)-symmetric bond-Boson model, which provides a particularly simple example for the concept of SO(5) symmetry. Based on this representation we show that antiferro- magnetism on one hand and superconductivity on the other hand can be understood as condensation of either magnetic or charged Bosons into an RVB vacuum. We identify exact eigenstates of a finite cluster with general multiplets of the SO(5) group, and present numerical results for the single particle spectra and spin/charge correlation functions of the SO(5)-symmetric model and identify `fingerprints' of SO(5) symmetry in these. In particluar we show that SO(5) symmetry implies a `generalized rigid band behavior' of the photoemission spectrum, i.e. spectra for the doped case are rigorously identical to spectra for spin-polarized states at half-filling. We discuss the problem of adiabatic continuity between the SO(5) symmetric ladder and the actual t-J ladder and demonstrate the feasibility of a `Landau mapping' between the two models.